Comparison of the percentage incidence of the organisms which have to be found associated with bronchiectasis and with purulent bronchitis unaccompanied by bronchiectasis shows that there is no noteworthy difference in the occurrence of pneumococci, hemolytic streptococci or B. influenzæ within the bronchi. When allowance is made for the difficulty of demonstrating B. influenzæ in the presence of a large number of other microorganisms, it is not improbable that this organism has been constantly present in the purulent contents of the bronchi with purulent bronchitis, with and without bronchiectasis. Pneumococci, streptococci and staphylococci are each present in the bronchi in about one-half of the instances of bronchiectasis and mixed infections are very common, S. viridans, B. coli and M. catarrhalis being occasionally found in the bronchi. The table shows that pneumococci, streptococci and staphylococci show no greater tendency to enter the lungs and blood when bronchiectasis and purulent bronchitis coexist than with purulent bronchitis alone.

Moderate dilatation of the small bronchi at the base of the left lung was found in several instances eight days after onset of symptoms referable to the respiratory passages. Advanced, diffuse dilatation of the bronchi was seldom seen before the lapse of two weeks, and bronchiectasis with formation of spherical or cylindrical cavities was found with few exceptions three weeks after onset of the fatal illness. Long continued, purulent bronchitis does not necessarily produce dilatation of the bronchi. It is noteworthy that the average duration of the fatal illness in 137 instances of pneumonia and purulent bronchitis with no bronchiectasis was 12.5 days, whereas the average duration of 49 instances of pneumonia with purulent bronchitis and bronchiectasis was only 16.5 days.

Bronchiectasis is almost invariably associated with purulent bronchitis in which tenacious mucopurulent fluid accumulates in the bronchi. It begins at the bases of the lower lobes and is usually more advanced here than elsewhere. Mechanical distention of the small bronchi by viscid fluid, expelled with difficulty, brings about their dilatation and gravity appears to have a part in accentuating the process. Histologic examination of the changes accompanying bronchitis show that lesions which penetrate into the muscular layer and presumably weaken the bronchial wall are not uncommon and partial or complete destruction of the wall may result. To what extent infiltration of the muscular wall by polynuclear leucocytes or by lymphoid and plasma cells is accompanied by changes which weaken the wall may be questioned. When the epithelial lining of the bronchus is destroyed coagulative necrosis of the underlying tissue occurs and may extend a variable distance into the bronchial wall, not infrequently penetrating into or entirely through the muscular layer. These changes furnish an explanation of the occurrence of bronchiectasis following influenza.

Acute bronchiectasis may be found following influenza after the illness has lasted eight or ten days. There is no increase of fibrous tissue. Small bronchi with no cartilage, which in normal lungs have a diameter approximating 1 mm., are dilated to 3 mm. or more. The surface epithelium is wholly or partially lost. Necrosis occurs in places and extends deep into the tissue, destroying muscle and often penetrating the entire thickness of the wall which in these small bronchi consists in large part of fibrous tissue containing greatly engorged blood vessels. In this necrotic material nuclei are absent and the tissue containing fibrin stains deeply with eosin. In it occur fissures or tears which extend from the lumen a variable distance, very frequently penetrating the entire thickness of the wall and entering adjacent alveoli (Figs. 17 and 19). Alveoli thus exposed almost invariably contain plugs of dense fibrin. Where these rents have occurred, adjacent edges of the bronchial wall, held together by underlying lung tissue, have separated from one another, so that the circumference of the bronchus has been increased (Fig. 18). These breaks in the continuity of the wall may occur in several places, so that a fourth or a third of the circumference may be formed by exposed alveolar tissue which has become the site of fibrinous pneumonia (Fig. 20). During life, though the inflamed bronchus is filled by mucopurulent exudate, distention of loose alveolar tissue, uniting the interrupted bronchial wall, is doubtless greater than it appears in the lung fixed by hardening fluids.

Recently dilated bronchi have an irregularly stellate lumen as the result of clefts penetrating at intervals into or through the bronchial wall (Fig. 26). Longitudinal fissures mark the lining of these dilated bronchial tubes.

When the fatal illness has lasted more than two weeks, abundant new formation of fibrous tissue occurs in a zone surrounding the dilated bronchus. Adjacent alveolar walls are thickened by young fibrous tissue. Alveoli, much diminished in size, are filled by hyaline fibrin into which fibroblasts and newly formed blood vessels have penetrated. These changes are limited to a wide zone in immediate contact with the dilated bronchus, whereas at a greater distance alveolar walls have undergone no thickening and alveoli contain no fibrin.

This stage is well represented by Autopsy 421 after an illness of nineteen days. Bronchiectatic cavities, from 3 to 6 mm. in diameter, are numerous in sections of the lung; their lumina are irregular in outline and often irregularly stellate. Microscopic examination shows the presence of clefts which interrupt the bronchial wall at intervals throughout its entire circumference. The original wall is well indicated by the very richly vascularized connective tissue containing scattered muscle bundles and is infiltrated with lymphoid and plasma cells in great number. Where fissures have occurred the adjacent edges of the interrupted wall have separated from one another, leaving a wide interval where underlying alveolar tissue is exposed. Two changes tend eventually to render the fissures inconspicuous, namely, regeneration of epithelium and new formation of fibrous tissue. Exposed alveoli filled with fibrin are in process of organization and epithelium which has assumed a squamous type has grown down over the exposed surfaces of the interrupted bronchial wall. It has begun to cover or in some instances has completely covered the surface of rents entering alveoli plugged with fibrin (Fig. 21). In the periphery of the bronchus alveolar walls are thickened and infiltrated with lymphoid and plasma cells. The same changes affect bronchi containing cartilage which is undergoing atrophy.

The reinforcement of the fissured bronchial wall by new formation of fibrous tissue, by thickening of the interalveolar walls and by organization of fibrin within the alveoli is well shown after four weeks (Autopsy 425; Fig. 28). There are spherical bronchiectatic cavities more than a centimeter in diameter surrounded by a dense fibrous wall in which are atrophied alveoli lined by epithelium of cubical form. Occasionally, the fibrous wall is interrupted and alveoli, plugged with organizing fibrin, are in immediate contact with the lumen. When these plugs of fibrin which are slowly absorbed disappear, evidence of preexisting rents in the bronchial wall are lost, and there are in this lung bronchiectatic cavities of which the wall is a continuous circle of dense fibrous tissue.

Epithelium lining the dilated bronchi is at times completely destroyed (Fig. 28), but more frequently it persists in part. That which remains has almost constantly the character of squamous epithelium (Figs. 22 and 23). The lowermost cells are cubical; those above them are polygonal, tending to become flatter as the surface is approached; upon the surface are cells often much flattened and occasionally they have lost their nuclei and stain deeply with eosin as the result of superficial necrosis. The change should not be regarded as metaplasia, for the epithelium assumes this squamous type when the superficial columnar cells have been lost. Actual necrosis of superficial ciliated columnar cells is occasionally seen (Autopsy 352); injured cells have separated from one another and desquamated into the lumen of the bronchus. The epithelium which remains after the superficial cells are lost consists of cells which become flatter from base to surface, but the intercellular bridges characteristic of the epithelium of the skin are not found. When epithelium is in process of regeneration, a layer gradually diminishing in thickness extends over the denuded surface, the advancing edge being formed by very flat cells in a single layer. The epithelium growing into fissures which have penetrated the bronchial wall may completely cover the exposed alveolar tissue. The newly formed epithelium may follow a fissure into an alveolus which has been opened and come into contact with the fibrin which fills the alveolus.

Bronchiectasis usually affects the small bronchi with no cartilage. It is not uncommon to find greatly dilated bronchi with no cartilage in close proximity to cartilage containing bronchi of smaller caliber. In one instance (Autopsy 421) a bronchus of medium size with cartilage measured 3 mm. in diameter, whereas two bronchi with no cartilage were dilated to 4 and 6 mm., respectively. Nevertheless, larger bronchi are occasionally the site of superficial loss of epithelium, necrosis extending into the bronchial wall, formation of fissures and stretching of the wall at the spot which is weakened. In association with these changes atrophy of the cartilage may occur (Autopsies 421, 425, 440, 463). Plates of cartilage in process of atrophy are readily recognized by their irregularly indented outline and often by their small size. The fibrous tissue surrounding the cartilage is the site of chronic inflammation and is densely infiltrated with lymphoid and plasma cells among which polynuclear leucocytes are scant. Nevertheless, polynuclear leucocytes are abundant in immediate contact with the cartilage and appear to have an important part in the solution of its matrix, for about them occur indentations of the edge. Leucocytes penetrate into the cartilage.

The necrosis and tears which occur in the wall of the bronchus are not always limited to the bronchus, but may extend deeply into the surrounding tissue. In Autopsies 312 (Fig. 21) and 423 wide areas of necrosis have penetrated deeply into the tissue about the bronchi.

Autopsy 312.—Illness began with influenza on September 26, seventeen days before death; a diagnosis of lobar pneumonia with consolidation of the right lower lobe was made ten days after onset and Pneumococcus IV, B. influenzæ and S. hemolyticus were found in the sputum. At autopsy there was bronchopneumonia with red and gray lobular and confluent lobular patches of consolidation and right and left serofibrinous pleurisy; there was purulent bronchitis; no abscesses were seen. Small bronchi throughout both lungs were dilated and often surrounded by a zone of hemorrhage.

Hemolytic streptococci were found in the heart’s blood, in the pleural exudate, consolidated lung and bronchus; B. influenzæ was found in the lung and in a small bronchus, and staphylococci in the contents of a small bronchus.

Bronchi which are the site of acute inflammation have lost their epithelium wholly or in part, and deep fissures penetrate the entire thickness of the bronchial wall, extending into the surrounding lung tissue which is the site of fibrinous pneumonia. In some instances plugs of fibrin within the alveoli are bisected by these tears. There is some superficial necrosis along the edge of each fissure, in several places extending outward from defects in the walls of small bronchi dilated to approximately 1.5 mm. There are wide patches of necrosis affecting both alveolar walls and contents of alveoli and extending 2 mm. into the lung tissue. When a fissure has penetrated from the lumen of the bronchus into necrotic tissue (Fig. 21), polynuclear leucocytes have accumulated within the necrotic tissue, disintegration of tissue occurs, and a small cavity communicating with the bronchus is formed.

Autopsy 423.—C. H., white, aged twenty-five, resident of Oklahoma, had been in military service one month. Death occurred sixteen days after onset of influenza.

Anatomical Diagnosis.—Chronic bronchopneumonia with peribronchiolar consolidation throughout right lung and in left lower lobe; right purulent pleurisy; purulent bronchitis; bronchiectasis at base of left lung.

The right lung weighs 1,260 grams; in the upper lobe are yellowish gray nodules having the appearance of tubercles clustered about small bronchi; in places similar nodules occur upon a background of pinkish gray consolidation occupying the greater part of the lower lobe. Bronchi contain purulent fluid. The left lung weighs 760 grams; it is edematous and small, yellowish gray nodules of consolidation in the lower lobe are clustered about terminal bronchi. Bronchi at the base of the lower lobe are dilated.

Bacteriologic examination shows the presence of hemolytic streptococci in the blood of the heart; hemolytic streptococci and B. influenzæ in the lung.

Microscopic examination shows that the walls of the bronchi are infiltrated with lymphoid and plasma cells; these cells are very numerous in peribronchiolar patches of consolidation. A small bronchus 1 mm. in diameter has squamous epithelium along one side; on the opposite side, the wall is completely absent and there is superficial necrosis of exposed alveoli filled with fibrin. A deep fissure passes from the bronchus into the consolidated tissue; its edges are necrotic and it is filled with polynuclear leucocytes. A small cavity in contact with the bronchus has been formed. In another part of the lung a distended bronchus has lost its epithelium on one side, and here alveoli filled with fibrin form the wall of the bronchus which is filled with leucocytes. Extending outward from the eroded wall is a focus of necrosis where both alveolar walls and contained exudate have lost their nuclei.

The necrosis which has had its origin in the bronchi is soon followed by accumulation of polynuclear leucocytes, softening and disintegration of tissue. Discharge of the disintegrated tissue through the bronchi results in the formation of a small cavity continuous with the bronchus. These changes are well illustrated by the bronchiogenic abscesses which have been described elsewhere (Autopsies 376, p. 206, and 387, p. 206). When disintegrated tissue is discharged by way of the bronchi no accumulation of pus occurs, but cavities will be formed, in part by dilation of bronchi, in part by erosion of the adjacent lung tissue. Histologic examination shows that these changes have produced the advanced bronchiectasis found in Autopsy 445 (Fig. 25).

Autopsy 445.—W. F., white, aged twenty-three, from Mississippi, had been in military service one month. His illness began September 22, twenty-seven days before death, with severe coryza, weakness, nausea and vomiting; great pain in bones, cough and sore throat. He was admitted to the base hospital one week later with diagnosis of influenza and bronchitis. On October 3, sixteen days before death, signs of consolidation were found on the left side over the back and a diagnosis of lobar pneumonia was made. On October 18 there was severe headache, pupils were dilated, and there was rigidity of neck; lumbar puncture was made and pneumococci were found in the fluid obtained. Death occurred on the following day.

Anatomic Diagnosis.—Bronchiectasis with unresolved pneumonia limited to the left lower lobe; acute bronchopneumonia with peribronchiolar consolidation in right lung; purulent bronchitis, peribronchial hemorrhage and organizing bronchiolitis in right lung; adherent pleura on left side; purulent meningitis.

The left upper lobe is crepitant throughout. The outer and posterior two-thirds of the left lower lobe is riddled with cavities often rounded and varying in diameter from 0.5 to 3 cm. but not infrequently irregular in shape and in communication with adjacent cavities (Fig. 25). In places cavities pass in a tortuous course from pleura to the midpart of lung. The lining of these cavities is usually smooth, but in places is covered by gray necrotic material. Communication between the cavities and medium-sized bronchi is occasionally found. The lung tissue between the cavities is in part grayish red and consolidated, in part pink and air containing. The right lung is edematous throughout; the bronchi in the lower part of the right lung contain purulent fluid and are in places surrounded by zones of hemorrhage.

The spleen is very large (14 × 11 × 5 cm.) and firm.

The spinal fluid is cloudy and blood vessels over the lumbar enlargement and lower thoracic region are congested; in the upper thoracic region the cord is covered by purulent exudate.

Bacteriologic examination demonstrates the presence of hemolytic streptococci in the blood of the heart; plates from the left lung contain a few colonies of S. aureus and Pneumococcus IV; plates from the right main bronchus contain S. aureus and a large bacillus which does not stain by Gram’s method. Three plates from the spinal meninges contain Pneumococcus IV.

Microscopic examination shows that the cavities which have been described are lined by very vascular connective tissue containing many cells; there is no epithelial lining and the surface is in places covered by fibrin. On the surface polynuclear leucocytes are numerous, but immediately below, large mononuclear cells occur and frequently contain one or several ingested polynuclear leucocytes. None of the structures peculiar to the bronchi can be identified in the wall of these cavities, and in many places it is evident that lung tissue has undergone destruction, for in places the lining of vascular connective tissue is interrupted and an extension of the cavity penetrating into the lung substance is surrounded by alveoli filled with fibrin; in contact with the cavity there is some necrosis.

The cavities communicate with the bronchi and are lined in part by vascular connective tissue which may in part represent preexisting bronchial walls, but no epithelium is present and the relation to the bronchi cannot be established with certainty. These cavities have extended by necrosis which has broken the vascular connective tissue of their wall and penetrated into adjacent lung tissue. Death has been the result of purulent meningitis caused by pneumococcus, and the histologic changes in the walls of the cavities suggest that the activity of the inflammatory reaction here is subsiding, for large mononuclear cells are numerous and are ingesting polynuclear leucocytes. The changes described would, if continued, result in the formation of cavities lined by fibrous tissue and resembling many of those formed as the result of dilatation of the bronchi.

A study of the progress of the changes which result in the formation of bronchiectatic cavities has shown how the inflammatory irritant within the bronchus destroys the epithelium of the bronchus, penetrates into the deeper tissues and produces fissures which extend through the entire thickness of the bronchial wall at one or usually several places. These longitudinal fissures, which at first often give a stellate outline in cross section to the cavity of the affected bronchus, permit the separation of the edges of the fissure, so that an increase in the circumference occurs. The base of the fissure is formed by surrounding alveolar tissue and its edges are the site of necrosis. Tears may extend into the surrounding alveolar tissue, thus permitting further stretching of the bronchial wall. The consequences of rupture of the small bronchi into the adjacent alveoli are to some extent overcome by the inflammatory reaction which plugs the adjacent alveoli with fibrin.

Compression of the lungs by forced expiration, even though the glottis were closed as in coughing, would not dilate the bronchi, because pressure outside and within the bronchi would be equally elevated (Thornton and Pratt^[89]). The pressure within the bronchi does not differ greatly from atmospheric pressure, whereas the negative pressure within the pleural cavity may vary from approximately 6 mm. of mercury during quiet inspiration to 30 mm. with forced inspiration. Excess of pressure upon the inner surface of the bronchial walls will vary with coughing and other respiratory efforts, between these limits depending upon the readiness with which pressure is equalized within and without the bronchi by penetration of air into the alveoli. The presence of viscid mucopurulent fluid within bronchioles will obstruct these tubules and retard the entrance of air into alveoli.

Weakening of the bronchial wall by the changes which have been described will cause lasting dilatation of the bronchi. Whatever increases pressure within the bronchi will increase the tendency to dilatation; the bronchi being filled with mucopurulent exudate dilatation usually appears first at the bases of the lung, since gravity increases intrabronchial pressure here. New formation of fibrous tissue within the wall of the bronchus, thickening of adjacent alveolar walls, and organization of fibrin reinforce the weakened bronchial wall and limit the dilatation which follows injury to the wall. Regeneration of epithelium covering the dilated tube will further obscure the early changes which have made dilatation possible. The changes which weaken the bronchial wall permit dilatation at a time when there is no new formation of fibrous tissue. When the bronchial lesion has persisted several weeks, chronic pneumonia is associated with it. It has been suggested that the contraction of newly formed fibrous tissue within the substance of the lung might cause bronchi to be enlarged by traction upon their walls. Newly formed connective tissue is most abundant in the wall of the bronchiectatic cavity, and here contraction would tend to diminish the size of the cavity.

Unresolved Bronchopneumonia

Chronic bronchopneumonia is characterized by changes similar to those associated with chronic inflammation in other parts of the body, namely, by thickening of the interstitial tissue of the lung, by accumulation of mononuclear cells, by proliferation of fibrous tissue and by organization of exuded fibrin. In a few instances these changes have begun at the end of two weeks after onset of influenza, but they have been little advanced until three weeks has elapsed; advanced chronic inflammation has occurred after from four to eight weeks. Chronic inflammation primarily affects those structures which are most severely injured by the acute lesion and is most conspicuous in immediate proximity to the small bronchi and bronchioles; the perivascular and interlobular connective tissue are secondarily involved. Corresponding to each of the lesions of the alveolar tissue which have been found with bronchopneumonia, namely, peribronchiolar, hemorrhagic peribronchiolar, lobular and peribronchial consolidation, there is a chronic lesion which develops when pneumonia has failed to resolve.

The term interstitial bronchopneumonia has been used by MacCallum to designate a lesion which he has found in association with measles at Fort Sam Houston. This name he states does not describe accurately the early stage of the lesion, for its interstitial character is not evident at first. In his monograph on “Epidemic Pneumonia in the Army Camp,” published in 1919, MacCallum describes and pictures instances of the lesion which we have designated interstitial suppurative pneumonia and classifies them as interstitial bronchopneumonia. We have shown that this lesion, which is the result of infection of the lymphatics with S. hemolyticus, bears no necessary relation to the lesion which is characterized in its early stage by peribronchiolar pneumonia and in its later stages by chronic inflammation with mononuclear infiltration and proliferation of the peribronchial, perivascular and interalveolar tissue. At Fort Sam Houston, nearly every patient with measles was infected with hemolytic streptococci; we observed, following influenza, similar prevalence of hemolytic streptococci in certain wards in the base hospital at Camp Pike. Among the cases at Fort Sam Houston there were doubtless instances both of interstitial suppurative pneumonia caused by hemolytic streptococcus and of chronic bronchopneumonia not referable to this microorganism.

Studying pneumonia following influenza at Camp Lee, Va., and later at Camp Dix, N. J., during the fall of 1918, MacCallum reached the conclusion that “interstitial bronchopneumonia” following influenza was caused by B. influenzæ of Pfeiffer. This lesion attributed to B. influenzæ differed from that previously referred to hemolytic streptococcus in the following characters: the lymphatic channels in the bronchial walls and widened interlobular septa are inconspicuous and none are found distended with exudate; there is no intense infection of the pleura, and polynuclear leucocytes are inconspicuous in the alveolar exudate and in the walls of the bronchi. It seems probable these differences are explained by the absence of hemolytic streptococci which tend to invade lymphatics and produce severe inflammatory changes in the pleura.

Chronic Bronchitis.—The earliest changes in the bronchial wall with bronchitis of influenza are hyperemia, leucocytic infiltration and hemorrhage, and they may occur even though the lining epithelium remains intact. Epithelium frequently undergoes partial or complete destruction, and with this severe injury the influence of the inflammatory irritant may extend directly through the wall of the bronchus, for in some instances there is hemorrhage into all the alveoli in a zone encircling the bronchus. Since these alveoli have only indirect communication with the affected bronchus through alveolar tissue not involved in the inflammatory process, it is evident that the surrounding hemorrhage is secondary to the lesion of the bronchus. Fibrinous inflammation in other instances, similarly localized in a zone of alveoli encircling a bronchus, is doubtless the result of direct extension of the inflammatory process through the bronchial wall. After the disease has existed during two or three weeks inflammation is still active immediately below the inner surface of the bronchus; here polynuclear leucocytes are numerous whereas in the deeper parts of the mucosa and about the muscularis leucocytes are scant but lymphoid and plasma cells are very numerous. The severity of the inflammatory reaction may be judged by the abundance and extent of this cellular reaction and is in close relation to the intensity of the changes affecting the mucous membrane of the bronchus. Infiltration of the entire bronchial wall with lymphoid and plasma cells is almost invariable when the primary injury to the bronchus has destroyed the epithelial lining, and this infiltration is not limited to the bronchial wall but extends outward into the contiguous alveolar septa which are thickened by it. The sheath of the pulmonary artery which accompanies the bronchus exhibits a similar change, and the alveolar septa, as a fringe about it, are thickened and infiltrated with mononuclear cells. Interlobular septa continuous with the bronchus often show some infiltration.

A later phase in this series of changes is represented by new formation of fibrous tissue. The bronchial walls and interalveolar septa are thickened by proliferating fibrous tissue, young fibroblasts and newly formed collagen fibrils being abundant (Fig. 28; also Fig. 30). This increase of fibrous tissue is especially noteworthy immediately surrounding the walls of the small bronchi, which are often considerably dilated, and about the smaller of those bronchi which have cartilage; with thickening of alveolar walls immediately adjacent to the bronchus every stage in the obliteration of the alveoli may be found. Their walls are thickened and their lumina are diminished in size and often flattened in a direction concentric with the bronchus. Such atrophied alveoli lined by cubical epithelial cells occurring within the thickened peribronchial fibrous tissue give evidence that this tissue has replaced alveoli. Alveoli surrounding and within the new fibrous tissue are frequently filled with fibrin, and organization indicated by penetration of fibroblasts and capillaries into the fibrin may be far advanced. There is some increase of perivascular and interlobular tissue. The bronchiectasis which is almost invariably found with unresolved bronchopneumonia has been described. Squamous transformation of epithelium (page 251) is frequently found in association with the chronic bronchitis of unresolved pneumonia.

Organizing Bronchitis and Bronchiolitis.—When the bronchial epithelium is destroyed, fibrin is deposited upon the denuded surface and may partly or completely fill the lumen of the bronchial tube. The plug of fibrin is adherent to the underlying tissue wherever epithelium is lost but is separated from the bronchial wall by a well-defined space where epithelial lining is still intact. Fibroblasts promptly migrate from the wall of the bronchiole into this fibrin, and fibroblasts, fixed during ameboid movement, are irregularly elongated in a direction toward the fibrin.

Organization of fibrin occurs within the smallest bronchi (diameter 0.3 to 0.5 mm.) or within respiratory bronchioles. It has been found in 8 autopsies. In one instance it has been present eleven days after the onset of influenza, but usually it is seen three or four weeks after onset of symptoms of respiratory disease. In the early stages of the lesion a plug of fibrin within the lumen of the bronchus or bronchiole is invaded by fibroblasts, plasma cells and newly formed capillaries. These capillaries have their origin in the wall of the tube and enter the fibrin at points where in consequence of loss of epithelium fibrin is continuous with the connective tissue. When the bronchiole is cut longitudinally, partially or completely organized fibrin may be found adherent at several places with intact epithelium, sometimes beautifully ciliated, between the sites of attachment. The fibrin is finally replaced completely and the lumen of the bronchiole contains a mass of organized fibrous tissue in which young fibroblasts and plasma cells are numerous.

The lesion has been associated with chronic bronchopneumonia in 6 of 8 instances. In Autopsy 445, p. 257, organizing bronchitis and bronchiolitis occurred in the right lung unassociated with other chronic lesion, although there was advanced bronchiectasis with fibrous induration in the left lung. In Autopsy 499 (p. 224) organizing bronchiolitis occurred in association with chronic changes which appear to have followed interstitial suppurative pneumonia caused by S. hemolyticus. Other severe lesions of the bronchi have accompanied organizing bronchitis and bronchiolitis. Purulent bronchitis has been present in 7 of 8 instances; bronchiectasis in 5 of 8 instances.

The bacteriology of autopsies with organizing bronchitis and bronchiolitis is shown in Table LIII.

The bacteriology of these cases presents no constant feature. Invasion of the blood by S. hemolyticus has been present in a large proportion of cultures, namely, in 5 of 7 (71.4 per cent). In one of the 2 instances in which hemolytic streptococci have been found, neither in the blood nor lungs, Pneumococcus III has been found in the blood and S. viridans in the lungs and bronchus; in the other, S. aureus has been found in the lung and bronchus. Staphylococci have been found frequently in the bronchi (60 per cent) and in the lungs (50 per cent). B. influenzæ has been present in the bronchi in the usual proportion of instances (80 per cent). The lesion has occurred in the presence of B. influenzæ combined with streptococci or staphylococci.

Thrombosis of lymphatics in the wall of bronchi adjacent to blood vessels and in interlobular septa occurs, and occasionally organization of the fibrinous plug within the lymphatic is in progress (Autopsies 283, 425 and 463). Fibroblasts and capillaries penetrate from the wall of the lymphatic into a mass of hyaline fibrin which fills the lumen.

Unresolved Bronchopneumonia.—The most common type of pneumonic lesion following influenza is characterized by acute inflammation of the alveoli immediately adjacent to the bronchioles and the lesion is associated in many instances with hemorrhage or edema. If this lesion persists unresolved during several weeks, evidences of chronic inflammation are found. Peribronchial, perivascular and interlobular connective tissue is thickened and richly infiltrated with lymphoid and plasma cells, large mononuclear cells and many young fibroblasts. Interalveolar septa adjacent to the walls of bronchi and between alveoli surrounding inflamed bronchioles are implicated in the process. Interstitial changes characterize the lesion only in its late stage. It appears undesirable to give the name “interstitial pneumonia” to the early stage of a lesion which begins and in most instances terminates as an acute relatively superficial inflammation of the bronchi, bronchioles and peribronchiolar alveoli.

Chronic bronchopneumonia is often overlooked at autopsy because newly formed connective tissue is not present in sufficient quantity to attract attention (Fig. 26). When the lesion is advanced conspicuous gray white patches of fibrous tissue may be seen about the bronchi (Autopsy 487; Fig. 27) and interlobular septa may be obviously thickened (Autopsy 472). The most distinctive feature of the lungs is the presence of small, firm, gray or yellowish gray nodules of consolidation which resemble miliary tubercles. They represent the peribronchiolar patches of bronchopneumonia present during the acute stage and have assumed the well-defined outline and firm consistence of tubercles because polynuclear leucocytes and red blood corpuscles have in large part disappeared, interstitial tissue is increased, and exudate is in process of organization. These nodules are grouped in clusters about the small bronchi.

With unresolved bronchopneumonia the lungs are very voluminous and fail to collapse after they are removed from the chest and in some instances even after incision. The air containing tissue is usually dry. In our autopsies the lungs have been pink in color and often free from coal pigment, because those suffering with pneumonia have been in considerable part men from rural districts. Thick mucopurulent material exudes from the small bronchi which have been cut across; purulent bronchitis has been present in 20 of 21 instances of chronic bronchopneumonia. Bronchiectasis has been present in 13 instances; dilatation is often advanced, so that throughout the lungs are found bronchi with no cartilage distended to a diameter of 0.5 cm. In addition to the firm peribronchiolar tubercle-like nodules of consolidation there are scattered patches of gray lobular or confluent lobular consolidation. Yellowish nodules, grouped about bronchi and resembling those found elsewhere in air containing tissue, are occasionally seen scattered upon the cut surface of a patch of gray, confluent lobular consolidation (Autopsies 421, 423, 431).

Microscopic examination demonstrates the presence of those changes which have been described in association with chronic bronchitis and bronchiectasis. There is abundant new formation of fibrous tissue about the bronchi of small and medium size, thickening of adjacent interalveolar walls and incorporation of alveoli into the thickened bronchial wall (Figs. 27, 28, 30, and 31). In half of the instances of chronic bronchopneumonia there has been peribronchial fibrinous pneumonia, and organization of fibrin within the alveoli is usually well advanced. In one instance (Autopsy 487; Figs. 27 and 28) after an illness of fifty-five days this process has resulted in the formation of conspicuous patches of firm, grayish white fibrous tissue surrounding dilated bronchi. Organization of fibrinous exudate within the lung has not been limited to the alveoli but has occurred in the bronchioles as well. Organizing bronchiolitis has been present in 5 instances (Autopsies 370, 402, 457 and 473).

Increase of fibrous tissue occurs about the blood vessels and in the septa between the lobules, which are infiltrated with mononuclear wandering cells and fibroblasts. Dilatation and thrombosis of the lymphatic vessels have occurred in both situations, and in 3 instances (Autopsies 283, 425 and 463) organization of these fibrinous thrombi has occurred.

Thickening, cellular infiltration and fibrosis of the bronchial walls with interstitial inflammation and fibrosis of immediately adjacent alveolar septa are found about the ramifications of the bronchial tree and may be followed to the smallest bronchi. When the respiratory bronchioles are reached it will be found that the alveoli which stud their walls are implicated in the change. The fibrin which they contain is infiltrated with lymphoid and plasma cells, and with progress of the lesion is invaded by fibroblasts and capillaries. Infiltration and fibroid thickening extends from the bronchiolar wall to the alveolar septa continuous with it (Fig. 31 with measles). Similar changes occur about the alveolar ducts, and about the orifices of the tributary infundibula (Fig. 32), peribronchiolar foci of acute inflammation having assumed the characters of a chronic inflammatory process. Fibrin within the alveoli contains round cells and fibroblasts. With thickening of alveolar walls the alveolar lumina may be much diminished in size and often persist as spaces lined by cubical cells. Polynuclear leucocytes are usually numerous within the alveolar duct and in a few alveoli immediately adjacent to it, but elsewhere throughout the focus of inflammation round cells are predominant. The changes which have been described correspond with the transformation of ill-defined, gray or reddish gray spots of consolidation grouped about the terminal bronchi into firm sharply defined grayish white nodules having the consistence and appearance of miliary tubercles.

One of the most constant characters of pneumonia following influenza is its hemorrhagic character. In the earlier stages of pneumonia phagocytosis of red blood corpuscles by large mononuclear cells is frequently seen. In association with the chronic changes which have been described, large mononuclear cells filled with brown pigment, doubtless formed from red corpuscles, are often found within the alveoli. These pigment containing cells are similar to those commonly associated with chronic passive congestion of the lungs.

In one instance (Autopsy 457) hemorrhagic peribronchiolar pneumonia has been found in process of organization. The bronchioles and alveoli adjacent to them contain polynuclear leucocytes, but intervening alveoli almost uniformly contain blood and are the site of new formation of connective tissue. Interalveolar septa are thickened and alveoli which are lined by cubical epithelium are often diminished in size. In many places fibroblasts have penetrated in considerable number into the blood within the alveoli and occasionally newly formed capillaries are found within them.

Lobular patches of pneumonia are often found in process of organization (Autopsies 370, 421, 423, 433, 463, 472 and 473). Microscopic examination shows that whole lobules well defined by thickened septa are the site of chronic interalveolar inflammation and intraalveolar organization of exudate, whereas adjacent lobules are air containing and relatively normal. In the earlier stages of the process fibrin present within the alveoli is invaded by fibroblasts, mononuclear wandering cells and blood vessels but in the later stages fibrin has disappeared; the lumina of the alveoli are occupied by cellular fibrous tissue and in places the thickened alveolar walls and intraalveolar fibrous tissue have been fused to form wide patches of new tissue.

With chronic bronchopneumonia confluent lobular consolidation occasionally has a gray ground upon which are scattered small yellow spots clustered about the small bronchi (Autopsies 421, 423 and 431). Microscopic examination has shown that the yellowish spots correspond to dilated bronchioles filled with purulent exudate and surrounded with alveoli containing many polynuclear leucocytes. In the interstitial tissue about the bronchiole and between adjacent alveoli plasma cells are often present in great number. Between these spots of subacute bronchiolar inflammation lung tissue is the site of interalveolar proliferation of fibrous tissue and intraalveolar organization of exudate.

In all instances of chronic bronchopneumonia there has been peribronchial pneumonia in a zone encircling small bronchi with no cartilage and the smallest of the bronchi which have cartilage in their wall; thickening of interalveolar septa, organization of peribronchial fibrinous pneumonia and partial disappearance of alveoli have been described. In the following autopsy peribronchial fibroid pneumonia has been so advanced that conspicuous patches of gray white tissue surrounding bronchi have replaced in some parts of the lung a considerable part of the lung substance.

Autopsy 487.—W. C., white, aged twenty-seven years, a farmer from Mississippi had been in military service twenty-one days. Illness began on September 17, fifty-five days before death, with chill, fever, cough, backache, pain in the chest and coryza. The patient was admitted two weeks after onset with the diagnosis of influenza. Eight days later his sputum was blood tinged and there were signs of bronchopneumonia. One month after admission the patient developed a rash and a diagnosis of scarlet fever was made.

Anatomic Diagnosis.—Chronic bronchopneumonia with peribronchial fibroid induration; bronchiectasis; purulent bronchitis; abscesses at the bases of both lungs; seropurulent pleurisy on the left side.

The body is much emaciated. The left pleural cavity contains 650 c.c. of opaque, dull yellow, thin, purulent fluid. The surface of the left lung is covered in spots by white partially organized fibrin.

On section of the right lung (Fig. 27) the tissue is found in great part air containing but there are numerous firm, gray patches, irregular in shape and from 1 to 2 cm. across. In these spots the tissue is tough and resembles fibrous tissue; within them are much dilated bronchi. In the central part of the upper lobe is a group of cavities with smooth wall, the largest of these cavities being 12 mm. in diameter; immediately adjacent are dilated bronchi. Between and surrounding these cavities is gray tissue, like that described above. Below the outer surface of the upper lobe is an extensive area 7 cm. from above downward, thickly studded with bronchiectatic cavities, in the walls of which there is tough fibrous tissue. In the middle lobe are several dilated bronchi, the largest of which is 7 mm. in diameter, and elsewhere occur dilated bronchi with thickened walls. At the base of the lung below the pleura are two abscesses, which are yellow in the center and surrounded by hemorrhagic tissue. At the posterior part of the lower lobe there are numerous firm, nodular, yellowish spots grouped in clusters upon a background of red, air containing tissue. The bronchi throughout the lung contain mucopurulent fluid.

In the left lung patches of fibrous tissue are more numerous than on the right side and are irregular in shape, from 1 to 2 cm. across and most abundant in the center of the upper lobe. This fibrous tissue is in great part gray but in places it has a yellowish tinge. The bronchi everywhere are moderately dilated. At the base of the lung below the pleura is an abscess.

The other organs show no noteworthy change.

Bacteriologic Examination.—The fluid in the left pleura and right main bronchus contain S. hemolyticus. B. influenzæ is found in the right lung and right main bronchus.

Microscopic examination shows that the patches of dense fibrous tissue seen at autopsy almost invariably surround dilated bronchi with no cartilage in their walls (Fig. 28) and with a diameter of from 1 to 2 or more millimeters. These bronchi have lost their epithelial lining; they contain polynuclear leucocytes, and their wall in contact with the lumen is infiltrated to a varying distance with the same cells. Their inner surface is very irregular, and superficial necrosis occurs. The limits of the preexisting bronchial wall is no longer recognizable in the dense surrounding fibrous tissue richly infiltrated with lymphoid and plasma cells. In contact with the bronchus, often in a wide zone, all traces of alveoli have been destroyed, but further outward alveoli are represented by spaces lined by cubical epithelium. At the periphery of the zone of fibroid induration alveolar walls are much thickened and richly infiltrated with mononuclear wandering cells; the lumina of the alveoli contain plugs of organized fibrous tissue often covered by flat or cubical epithelium. In the surrounding tissue a few small bronchi are lined by columnar epithelium; there is scant new formation of fibrous tissue but the alveolar walls are thickened and infiltrated with cells. Epithelium of the larger bronchi with cartilage in their walls is usually intact and there is about them little peribronchial inflammation.

Advanced induration about the bronchioles represents a late stage of chronic peribronchiolar pneumonia. A bronchiole cut transversely is found in the center of a focus of induration situated within relatively normal air containing lung tissue. Next the bronchiole which in some instances has wholly or partly lost its epithelium there is very cellular fibrous tissue; further from the bronchiole alveoli are much diminished in size, lined by flat or cubical epithelium and separated by thick cellular walls. Plugs of cellular fibrous tissue sometimes fill the alveolar duct. In favorable sections, cut in a plane which shows the alveolar duct opening out into infundibula, it is found that newly formed fibrous tissue surrounds the alveolar duct and extends into the walls of its tributary alveoli; alveoli may be obliterated by this fibrous tissue. Induration of alveolar walls is evident along the proximal part of the infundibula which are readily demonstrable because they are much dilated. (See Fig. 32.) The distal parts of the infundibula are surrounded by alveoli with delicate walls.

One bronchus retains along one side part of its epithelium which has assumed a squamous form. In other places the wall has undergone necrosis which at one spot extends deeply into the surrounding tissue. Necrotic tissue in another part of the circumference is infiltrated with polynuclear leucocytes and separated from the surrounding tissue by a space filled with leucocytes. An abscess communicating with the bronchus is thus formed.

The foregoing instance is an example of the chronic fibroid pneumonias with bronchiectasis which occur as sequelæ of the epidemic of influenza. It is not improbable that a considerable number of those who suffer with chronic bronchitis and bronchiectasis following influenza have less extensive lesions similar to those which have been described.

Bacteriology of Unresolved Bronchopneumonia.—Bacteria found in the bronchi in 10 instances of chronic bronchopneumonia have been as follows:

Bacteria found in the lungs in 17 instances of chronic bronchopneumonia were as follows:

A noteworthy feature of these lists is the multiplicity of microorganism found, namely, B. influenzæ, S. hemolyticus, pneumococcus, staphylococcus, S. viridans, B. coli, and M. catarrhalis. More than one microorganism is usually found in both bronchus and lung. In the one instance (Autopsy 472) in which B. coli alone has been found in the bronchus, B. coli and S. hemolyticus have been found in the lung and hemolytic streptococcus in the blood; it is evident that B. coli alone has not been responsible for the lesion. In one instance (Autopsy 487) B. influenzæ alone has been found in the lung but hemolytic streptococci have been found in the bronchus, pleura and blood of heart; with S. aureus alone in the lung (Autopsy 370), S. aureus, Pneumococcus IV and B. influenzæ have been found in the bronchus. With S. viridans alone in the lung (Autopsy 473), Pneumococcus III has been found in the pleura and in the blood of the heart and has doubtless had an important part in the production of pneumonia; S. viridans, M. catarrhalis and B. influenzæ have been found in the bronchus in this instance.

No single microorganism is associated with the lesions but combinations of B. influenzæ with hemolytic streptococci or staphylococci are common (over 50 per cent). In Autopsy 422 B. influenzæ and Pneumococcus atypical II have been present in the lungs. Among 10 instances in which cultures have been obtained from the bronchus B. influenzæ is found 8 times, and in the 2 instances in which it has not been identified B. coli has been present. B. influenzæ has seldom been found (Table XXVII) in the presence of B. coli, and it is not improbable that B. coli outgrows and obscures the presence of B. influenzæ.

Table LIV shows the per cent incidence of pneumococci, hemolytic streptococci, staphylococci and B. influenzæ in the bronchus, lung and heart’s blood with chronic bronchopneumonia and serves as an index of the readiness with which each of these microorganisms passes from bronchus to lung and from lung to the blood in this disease.

Comparison of Table LIV with the analogous figures for acute bronchopneumonia shows little noteworthy difference. Pneumococci are less frequently found in the lung (12.5 per cent) and in the blood (16.6 per cent) with chronic bronchopneumonia than with acute bronchopneumonia (lung 43.9 per cent; blood, 40.3 per cent). Hemolytic streptococci and staphylococci are not more frequently found with unresolved than with acute bronchopneumonia and failure to resolve cannot be referred to either or to both microorganisms, for bronchopneumonia not infrequently remains unresolved in their absence. B. influenzæ is present in the bronchi in at least 80 per cent of instances and perhaps in all; it is usually combined both in the lungs and in the bronchi with one of the pyogenic cocci.

The severity of the injury to the walls of bronchi resulting in continued infection with a variety of bacteria, appears to be the factor determining failure of resolution and the persistence of bronchopneumonia.

The Relation of Unresolved Bronchopneumonia to Interstitial Suppurative Pneumonia Caused by Hemolytic Streptococci.—Hemolytic streptococci have been present in a considerable proportion of those who have had unresolved bronchopneumonia and its occurrence in the bronchi, lung and blood of the heart indicates that it has had an important part in causing death. Unresolved bronchopneumonia, following measles, designated by MacCallum “interstitial bronchopneumonia” in a series of autopsies at Fort Sam Houston in the spring of 1918, was constantly associated with hemolytic streptococci. Among the lesions described as interstitial bronchopneumonia was at least one which was evidently what we have designated interstitial suppurative pneumonia. Lymphangitis was not infrequently found with “interstitial bronchopneumonia” following measles. At Camp Lee and Camp Dix, following the epidemic of influenza, MacCallum found “interstitial bronchopneumonia” with no hemolytic streptococci and noted that lymphatics in the interstitial septa were inconspicuous and that none was found distended with exudate; empyema was not present.

We have shown that interstitial suppurative pneumonia is an acute lesion caused by hemolytic streptococci. Unresolved bronchopneumonia is accompanied by chronic pneumonia and has no necessary relation to this microorganism.

In a foregoing section we have described instances of interstitial suppurative pneumonia unaccompanied by chronic changes, and in the present section we have described instances of unresolved bronchopneumonia with no infection by hemolytic streptococci. We have pointed out that the incidence of streptococcus infection with unresolved bronchopneumonia does not materially differ from that with acute bronchopneumonia even though the greater duration of the disease gives more opportunity for infection. In some of the autopsies made by MacCallum at Fort Sam Houston, lesions of streptococcus infection doubtless coexisted with unresolved bronchopneumonia.

In the 3 autopsies described below, interstitial suppurative pneumonia with empyema caused by hemolytic streptococcus occurs in association with unresolved bronchopneumonia.

Autopsy 420.—J. E. S., white, aged thirty-two years, born in England and resident of Los Angeles, Cal., had been in military service one month. Onset of illness began on October 3, eleven days before his death. He was admitted to the hospital on the following day with the diagnosis of influenza and acute bronchitis. Pneumonia believed to be lobar was recognized eight days after admission.

Anatomic Diagnosis.—Unresolved bronchopneumonia with hemorrhagic peribronchiolar consolidation in right lung; interstitial suppurative pneumonia with consolidation in left upper lobe; fibrinopurulent pleurisy; purulent bronchitis.

The left pleural cavity contains 200 c.c. of turbid yellow fluid in which are flakes of fibrin. In the inner and upper part of the left upper lobe there is an area of consolidation where the tissue has a cloudy, pinkish gray color and is finely granular on section. Here the interstitial septa are distended by edema, so that they are in places 0.5 c.c. across; in some spots they have a bright yellow color. In the posterior parts of the middle and lower lobes there is flabby consolidation where the tissue has a cloudy, red color with scattered ill-defined yellow spots.

Bacteriologic examination shows the presence of hemolytic streptococci in the blood of the heart; hemolytic streptococci with B. influenzæ and S. aureus in the left lung and S. hemolyticus with S. aureus in the right lung.

Microscopic examination shows that bronchi, bronchioles, alveolar ducts and the greater part of the infundibula are filled with polynuclear leucocytes, whereas the alveoli surrounding these structures contain fibrin. The walls of the small bronchi are thickened and contain mononuclear cells; the adjacent alveolar walls are similarly infiltrated and thickened and the fibrin within them is undergoing organization, being invaded by plasma cells, fibroblasts and newly formed blood vessels. In some sections interstitial septa are distended by edema and contain fibrin in abundance; in places the tissue contains polynuclear leucocytes closely packed together. There are lymphatics greatly distended by polynuclear leucocytes with some fibrin, lymphocytes and red blood corpuscles.

Autopsy 428.—D. B., white, aged twenty-five, a farmer from Oklahoma, had been in military service three weeks. Onset of illness was on September 21, twenty-five days before death, with fever, cough and mucopurulent expectoration. The patient was admitted with the diagnosis of acute bilateral bronchitis. Four days later bronchopneumonia was recognized, and subsequently there was otitis media and empyema; 600 c.c. of thin, purulent fluid were aspirated from the right chest three days before death.

Anatomic Diagnosis.—Unresolved bronchopneumonia; suppuration of interstitial tissue of upper right and lower left lobes; purulent bronchitis; fibrinopurulent pleurisy; thoracotomy wound at the base of the right chest; collapse of both lungs; serofibrinous pericarditis.

The left pleural cavity contains 550 c.c. of turbid seropurulent fluid in which are numerous flakes of soft fibrin. The right pleural cavity contains 150 c.c. of similar fluid. The mediastinum is edematous. The pericardial cavity contains 50 c.c. of yellow fluid.

The right lung is moderately collapsed. In the upper and lower lobes are small patches of red, lobular consolidation. The upper third of the upper lobe is laxly consolidated and near its inner surface the interstitial septa are thickened to from 1 to 1.5 mm. in width, and at intervals occur bead-like swellings from which creamy purulent fluid exudes upon the cut surface. In the left lung small patches of gray consolidation occur throughout the lower lobe and here the interstitial septa are thickened, beaded and contain purulent fluid.

Bacteriologic examination shows that the blood contains S. hemolyticus; from the right lung and from the right main bronchus hemolytic streptococci and B. influenzæ are grown.

Microscopic examination shows that the epithelium of the bronchi has undergone hypertrophy; the wall is infiltrated with lymphoid and plasma cells and thickened by new formation of fibrous tissue; there is similar thickening of adjacent alveolar septa and alveoli, often lined by cubical cells, are diminished in size. Connective tissue about the blood vessels and the interstitial septa are thickened and infiltrated with mononuclear cells. In parts of the lung the interstitial septa are edematous and contain polynuclear leucocytes, in some places in great number. Lymphatics are greatly dilated and filled with polynuclear leucocytes which in the center of some lymphatics have undergone necrosis. In one place a small abscess is in contact with a distended lymphatic. Lymphatics contain Gram-staining cocci in pairs and short chains, present in immense number where necrosis has occurred.

Autopsy 433.—B. J., white, aged twenty-seven, from Arkansas, has been in military service one month. Onset of illness was on September 28, nineteen days before death, with cough and expectoration. Pneumonic consolidation was recognized two days later and 20 c.c. of cloudy fluid were aspirated from the left chest on the same day. Hemolytic streptococci were found in a culture from the throat nine days before death.

Anatomic Diagnosis.—Unresolved bronchopneumonia with peribronchiolar and confluent lobular consolidation; interstitial suppuration of the right lower lobe; purulent bronchitis; fibrinopurulent pleurisy.

The right pleural cavity contains 700 c.c. of yellowish gray purulent fluid containing flakes of fibrin. The left pleural cavity contains seropurulent fluid localized over the external part of the lung.

The right lung is voluminous and free from consolidation save at the lower and posterior part of the lower lobe where the tissue is deep red and studded with firmer spots of yellow color clustered about the bronchi. In places the interstitial septa are thickened and yellow. Surrounding some of the bronchi near the apex of the left lung are red patches of consolidation.

Culture from heart’s blood remained sterile. S. hemolyticus was grown from right pleural cavity, and S. hemolyticus and B. influenzæ were grown from the right lung. Culture from the left lung contained S. aureus and contaminating microorganisms.

Microscopic examination shows the presence of peribronchiolar patches of pneumonia in which there are few polynuclear leucocytes and many lymphoid and plasma cells; the alveolar walls are thickened and infiltrated with mononuclear cells. In some sections the tissue is wholly consolidated and the site of advanced organizing pneumonia. Interlobular septa and connective tissue about blood vessels are thickened and cellular. Small bronchi have lost their epithelial lining, their walls are thickened and there is peribronchial organizing pneumonia. In some sections the lymphatics are immensely dilated and distended with polynuclear leucocytes. There is necrosis of the walls of the lymphatics and of the polynuclear leucocytes within the lumen.

In the discussion of acute bronchopneumonia it has been shown that S. hemolyticus is not infrequently a secondary invader of a pneumonic lesion perhaps caused by pneumococci. With progress of the disease hemolytic streptococci persist. In the autopsies with unresolved pneumonia just described, hemolytic streptococci have found their way into the lymphatics and produced suppurative lymphangitis with inflammation of the interstitial septa of the lung.