A Manual of Clinical Diagnosis

1. Absorptive Power of the Stomach.—This is a very unimportant function, only a few substances being absorbed in the stomach. It is delayed in most organic diseases of the stomach, especially in dilatation and carcinoma, but not in neuroses. The test has little practical value.

Give the patient, upon an empty stomach, a three-grain capsule of potassium iodid with a glass of water, taking care that none of the drug adheres to the outside of the capsule. At intervals test the saliva for iodids by moistening starch-paper with it and touching with yellow nitric acid. A blue color shows the presence of an iodid, and appears normally in ten to fifteen minutes after ingestion of the capsule. A longer time denotes delayed absorption.

Starch paper is prepared by soaking filter-paper in boiled starch and drying.

2. Motor Power of the Stomach.—This refers to the rapidity with which the stomach passes its contents on into the intestine. It is very important: intestinal digestion can compensate for insufficient or absent stomach digestion only so long as the motor power is good.

Motility is impaired to some extent in chronic gastritis. It is especially deficient in dilatation of the stomach due to atony of the gastric wall or to pyloric obstruction, either benign or malignant. It is increased in most conditions with hyperchlorhydria.

The best evidence of deficient motor power is the detection of food in the stomach at a time when it should be empty, e.g., before breakfast in the morning. When more than 60 c.c. of fluid are obtained with the tube one hour after a Ewald breakfast, deficient motility may be inferred.

Ewald's salol test is scarcely so reliable as the above. It depends upon the fact that salol is not absorbed until it reaches the intestine and is decomposed by the alkaline intestinal juices.

The patient is given 15 grains of salol with a test-breakfast, and the urine, passed at intervals thereafter, is tested for salicyluric acid. A few drops of 10 per cent. ferric chlorid solution are added to a small quantity of the urine. A violet color denotes the presence of salicyluric acid. It appears normally in sixty to seventy-five minutes after ingestion of the salol. A longer time indicates impaired motor power.

3. To Determine Size and Position of Stomach.—After removing the test-meal, while the tube is still in place, force quick puffs of air into the stomach by compression of the bulb. The puffs can be clearly heard with a stethoscope over the region of the stomach, and nowhere else.

If desired, the patient may be given a dram of sodium bicarbonate in solution, followed immediately by the same amount of tartaric acid, also in solution; or he may take the two parts of a seidlitz powder separately. The carbon dioxid evolved distends the stomach, and its outline can easily be determined by percussion.

CHAPTER V

THE FECES

As commonly practised, an examination of the feces is limited to a search for intestinal parasites or their ova. Much of value can, however, be learned from other simple examinations, particularly a careful inspection. Anything approaching a complete analysis is, on the other hand, a waste of time for the clinician.

The normal stool is a mixture of—(a) Water; (b) undigested and indigestible remnants of food, as starch-granules, particles of meat, plant-cells and fibers, etc.; (c) digested foods, carried out before absorption could take place; (d) products of the digestive tract, as altered bile-pigments, mucus, etc.; (e) products of decomposition, as indol, skatol, fatty acids, and various gases; (f) epithelial cells shed from the wall of the intestinal canal; (g) harmless bacteria, which are always present in enormous numbers.

Pathologically, we may find abnormal amounts of normal constituents, blood, pathogenic bacteria, animal parasites and their ova, and biliary and intestinal concretions.

The stool to be examined should be passed into a clean vessel, without admixture of urine. The offensive odor can be partially overcome with turpentine or 5 per cent. phenol. When search for Amoeba coli is to be made, the vessel must be warm, and the stool kept warm until examined; naturally, no disinfectant can be used.

1. Quantity.—The amount varies greatly with diet and other factors. The average is about 100 to 150 gm. in twenty-four hours.

2. Frequency.—One or two stools in twenty-four hours may be considered normal, yet one in three or four days is not uncommon with healthy persons. The individual habit should be considered in every case.

3. Form and Consistence.—Soft, mushy, or liquid stools follow cathartics and accompany diarrhea. Copious, purely serous discharges without fecal matter are significant of Asiatic cholera, although sometimes observed in other conditions. Hard stools accompany constipation. Rounded scybalous masses are common in habitual constipation, and indicate atony of the muscular coat of the intestine. Flattened, ribbon-like stools result from some obstruction in the rectum, generally a tumor or stricture from a healed ulcer, most commonly syphilitic. When bleeding piles are absent, blood-streaks upon such a stool point to carcinoma.

4. Color.—The normal light or dark-brown color is due chiefly to altered bile-pigments. The stools of infants are yellow, owing partly to their milk diet and partly to the presence of unchanged bilirubin.

Diet and drugs cause marked changes: milk, a light yellow color; cocoa and chocolate, dark gray; various fruits, reddish or black; iron and bismuth, dark brown or black; hematoxylin, red; etc.

Pathologically, the color is important. A golden yellow is generally due to unchanged bilirubin. Green stools are not uncommon, especially in diarrheas of childhood. The color is due to biliverdin, or, sometimes, to chromogenic bacteria. Putty-colored or "acholic" stools occur when bile is deficient, either from obstruction to outflow or from deficient secretion. The color is due less to absence of bile-pigments than to presence of fat. Similar stools are common in conditions like tuberculous peritonitis, which interfere with absorption of fats, and in pancreatic disease.

Notable amounts of blood produce tarry black stools when the source of the hemorrhage is the stomach or upper intestine, and a dark brown or bright red as the source is nearer the rectum. When diarrhea exists, the color may be red, even if the source of the blood is high up. Red streaks of blood upon the outside of the stool are due to lesions of rectum or anus.

5. Odor.—Products of decomposition, chiefly indol and skatol, are responsible for the normal offensive odor. A sour odor is normal for nursing infants, and is noted in mild diarrheas of older children. In the severe diarrheas of childhood a putrid odor is common. In adults stools emitting a very foul stench are suggestive of malignant or syphilitic ulceration of the rectum or gangrenous dysentery.

6. Mucus.—Excessive quantities of mucus are easily detected with the naked eye, and signify irritation or inflammation. When the mucus is small in amount and intimately mixed with the stool, the trouble is probably in the small intestine. Larger amounts, not well mixed with fecal matter, indicate inflammation of the large intestine. Stools composed almost wholly of mucus and streaked with blood are the rule in dysentery, ileocolitis, and intussusception. In the so-called mucous colic, or membranous enteritis, shreds and ribbons of altered mucus, sometimes representing complete casts of the bowel, are passed.

7. Concretions.—Gall-stones are probably more common than is generally supposed, and should be searched for in every case of obscure colicky abdominal pain. Intestinal concretions (enteroliths) are rare.

Concretions can be found by breaking up the fecal matter in a sieve (which may be improvised from gauze) while pouring water over it. It must be remembered that gall-stones, if soft, may go to pieces in the bowel.

8. Animal Parasites.—Segments of tape-worms and the adults and larvæ of other parasites are often found in the stool. They are best searched for in the manner described for concretions. The search should be preceded by a vermicide and a brisk purge. Patients frequently mistake vegetable tissue (long fibers from poorly masticated celery or "greens," cells from orange, etc.) for intestinal parasites, and the writer has known physicians to make similar mistakes. Even slight familiarity with the microscopic structure of vegetable tissue will prevent the chagrin of such errors.

Complicated chemic examinations are of little value to the clinician. Certain tests are, however, important.

1. Blood.—When present in large amount, blood produces such changes in the appearance of the stool that it is not likely to be overlooked. Traces of blood (occult hemorrhage) can be detected only by special tests. Recognition of occult hemorrhage has its greatest value in diagnosis of gastric cancer and ulcer. It is constantly present in practically every case of gastric cancer, and is always present, although usually intermittently, in ulcer. Traces of blood also accompany malignant disease of the bowel, the presence of certain intestinal parasites, and other conditions.

Detection of Occult Hemorrhage.—Soften a portion of the stool with water, treat with about one-third its volume of glacial acetic acid, and extract with ether. Should the ether not separate well, add a little alcohol. Apply the guaiac test to the ether as already described (p. 89).

In every case iron-containing medicines must be stopped, and blood-pigment must be excluded from the food by giving an appropriate diet, e.g., bread, milk, eggs, and fruit. At the beginning of the restricted diet give a dram of powdered charcoal, or 7 grains of carmin, so as to mark the corresponding stool.

2. Bile.—Normally, unaltered bile-pigment is never present in the feces of adults. In catarrhal conditions of the small intestine bilirubin may be carried through unchanged. It may be demonstrated by filtering (after mixing with water if the stool be solid) and testing the filtrate by Gmelin's method, as described under The Urine.

Care must be exercised in selection of portions for examination. A random search will often reveal nothing of interest. A small bit of the stool, or any suspicious-looking particle, is placed upon a slide, softened with water if necessary, and pressed out into a thin layer with a cover-glass. A large slide—about 2 by 3 inches—with a correspondingly large cover will be found convenient. Most of the structures which it is desired to see can be found with a two-thirds objective. Details of structure must be studied with a higher power.

The bulk of the stool consists of granular débris. Among the recognizable structures met in normal and pathologic conditions are: remnants of food, epithelial cells, pus-corpuscles, red blood-corpuscles, crystals, bacteria, and ova of animal parasites (Fig. 90).

1. Remnants of Food.—These include a great variety of structures which are very confusing to the student. Considerable study of normal feces is necessary for their recognition.

Vegetable fibers are generally recognized from their spiral structure; vegetable cells, from their double contour and the chlorophyl bodies which many of them contain. These cells are apt to be mistaken for the ova of parasites. Starch-granules sometimes retain their original form, but are ordinarily not to be recognized except by their staining reaction. They strike a blue color with Lugol's solution when undigested; a red color, when slightly digested. Muscle-fibers are yellow, and sometimes appear as short, transversely striated cylinders with rather squarely broken ends. Generally, the ends are rounded and the striations faint, or only irregularly round or oval yellow masses are found. Curds of milk are especially important in the stools of children. They must be distinguished from small masses of fat. The latter are soluble in ether, and stain red with Sudan III.

Excess of any of these structures may result from excessive ingestion or deficient intestinal digestion.

2. Epithelial Cells.—A few cells derived from the wall of the alimentary canal are a constant finding. They show all stages of degeneration, and are often unrecognizable. A marked excess has its origin in a catarrhal condition of some part of the bowel. Squamous cells come from the anal orifice; otherwise the form of the cells gives no clue to the location of the lesion.

3. Pus.—Amounts of pus sufficient to be recognized with the eye alone indicate rupture of an abscess into the bowel. If well mixed with the stool, the source is high up, but in such cases the pus is apt to be more or less completely digested, and hence unrecognizable. Small amounts, detected only by the microscope, are present in catarrhal and ulcerative conditions of the intestine, the number of pus-cells corresponding to the severity and extent of the process.

4. Blood-corpuscles.—Unaltered red corpuscles are rarely found unless their source is near the anus. Ordinarily, only masses of blood-pigment can be seen. Blood is best recognized by the chemic tests (p. 239).

5. Bacteria.—In health, bacteria constitute about one-third of the weight of the dried stool. They are beneficial to the organism, although not actually necessary to its existence. It is both difficult and unprofitable to identify them. The great majority belong to the colon bacillus group, and are negative to Gram's method of staining.

In some pathologic conditions the character of the intestinal flora changes so that Gram-staining bacteria very greatly predominate. As shown by R. Schmidt, of Neusser's clinic in Vienna, this change is most constant and most striking in cancer of the stomach, owing to large numbers of Boas-Oppler bacilli, and is of considerable value in diagnosis. He believes that a diagnosis of gastric carcinoma should be very unwillingly made with an exclusively "Gram-negative" stool, while a "Gram-positive" stool, due to bacilli (which should also stain brown with Lugol's solution), may be taken as very strong evidence of cancer. A Gram-positive stool due to cocci is suggestive of intestinal ulceration. The technic is the same as when Gram's method is applied to other material (p. 40), except that the smear is fixed by immersion in methyl-alcohol for five minutes instead of by heat. Fuchsin is the best counter-stain. The deep-purple Gram-staining bacteria stand out much more prominently than the pale-red Gram-negative organisms, and one may be misled into thinking them more numerous even in cases in which they are much in the minority. The number of Boas-Oppler bacilli can be increased by administering a few ounces of sugar of milk the day before the examination.

Owing to the difficulty of excluding swallowed sputum, the presence of the tubercle bacillus is less significant in the feces than in other material. It may, however, be taken as evidence of intestinal tuberculosis when clinical signs indicate an intestinal lesion and reasonable care is exercised in regard to the sputum. Success in the search will depend largely upon careful selection of the portion examined. A random search will almost surely fail. Whitish or grayish flakes of mucus or blood-stained or purulent particles should be spread upon slides or covers and stained by the method given upon p. 127. In the case of rectal ulcers, swabs can be made directly from the ulcerated surface.

6. Crystals.—Various crystals may be found, but few have any significance. Slender, needle-like crystals of fatty acids and soaps (Fig. 32) and triple phosphate crystals (Fig. 90) are common. Characteristic octahedral crystals of calcium oxalate (Fig. 47) appear after ingestion of certain vegetables. Charcot-Leyden crystals (Fig. 6) are not infrequently encountered, and strongly suggest the presence of intestinal parasites. Yellowish or brown, needle-like or rhombic crystals of hematoidin (Fig. 32) may be seen after hemorrhage into the bowel.

7. Ova of Parasites.—The stool should be well mixed with water and allowed to settle. The ova will be found in the upper or middle portions of the sediment. Descriptions will be found in the following chapter.

CHAPTER VI

ANIMAL PARASITES

Animal parasites are common in all countries, but are especially abundant in the tropics, where almost every native is host for one or more varieties. Because of our growing intercourse with these regions, the subject is assuming increasing importance in this country. Many parasites, hitherto comparatively unknown here, will probably become common.

Some parasites produce no symptoms, even when present in large numbers. Others cause very serious symptoms. Only those which have clinical interest will be considered here. The illustrations will give a better idea of their appearance than any description. They belong to three classes: I. Protozoa. II. Vermes. III. Arthropoda.

1. Amoeba Coli Dysenteriæ.—This organism is found, often in large numbers, in the stools of tropical dysentery and in the pus and walls of hepatic abscesses associated with dysentery, and is generally regarded as the cause of the disease. It is a colorless, granular cell, 20 to 40 µ in diameter (Fig. 91). It contains one or more distinct vacuoles; a round nucleus, which ordinarily is obscured by the granules; and frequently red blood-corpuscles and bacteria. When at rest, its shape is spheric; but upon a warm slide it exhibits the characteristic ameboid motion, constantly changing its shape or moving slowly about. This motion is its most distinctive feature. Other amebæ, resembling the pathogenic variety but smaller (10 to 15 µ in diameter), are sometimes found in normal feces.

When the presence of amebæ is suspected, the stool should be passed into a warm vessel and kept warm until and during the examination. A warm stage can be improvised from a plate of copper with a hole cut in the center. This is placed upon the stage of the microscope, and one of the projecting ends is heated with a small flame. Amebæ are most likely to be found in grayish or blood-streaked particles of mucus. Favorable material for examination can be obtained at one's convenience by inserting into the rectum a large catheter with roughly cut lateral openings. A sufficient amount of mucus or fecal matter will usually be brought away by it.

2. Trichomonas Vaginalis.—The acid discharge of catarrhal vaginitis sometimes contains this parasite in abundance. It is oval or pear-shaped, one to three times the diameter of a red blood-corpuscle in length, and has a cluster of flagella at one end (Fig. 92). It is not unlike a pus-corpuscle in size and general appearance, but is actively motile. When in motion the flagella are not easily seen. No pathogenic significance is ascribed to it. Other varieties of the genus have been found in the feces, the urine, and the sputum.

A similar but somewhat smaller organism, Cercomonas hominis (Fig. 93), has been found in the feces in a variety of diarrheal conditions and in from 10 to 25 per cent. of healthy persons in tropical regions.

In urine or vaginal discharges these organisms might be mistaken for spermatozoa by one who is entirely unfamiliar with the appearance of either.

3. Paramoecium Coli (Balantidium Coli).—This parasite is an occasional inhabitant of the colon of man, and sometimes produces diarrhea. It is an oval organism, about 0.1 mm. long, is covered with cilia, and contains a bean-shaped nucleus, two contractile vacuoles, and variously sized granules (Fig. 94).

4. Hemosporidia.—This is a large group of parasites with two life-cycles: one in the blood-corpuscles or plasma of a vertebrate host—man, mammals, birds, reptiles; the other in the body of some insect. The malarial parasite, already described; the organism (Pirosoma bigeminum) producing Texas fever in cattle; and the questionable parasite (Piroplasma hominis), which has been described as the cause of "tick fever" of Montana, belong to the group.

5. Trypanosomes have been mentioned (p. 195).

1. Cestoda.—Tape-worms are very common parasites of both man and the animals. The most important are Tænia saginata, Tænia solium, Bothriocephalus latus, and Tænia echinococcus. They all pass a larval stage in the body of an intermediate host. In the adult stage they consist of a linear series of flat, rectangular segments (proglottides), at one end of which is a smaller segment, the scolex or head, especially adapted for attachment to the host. The series represents a colony, of which the scolex is ancestor. The proglottides are sexually complete individuals, derived from the scolex by budding. With exception of the immature segments near the scolex, each contains a uterus filled with ova. The three tape-worms first mentioned are distinguished from one another mainly by the structure of the scolex and of the uterus (Fig. 100). The scolex should be studied with a low-power objective. The uterus is best seen by pressing the segment out between two plates of glass.

(1) Tænia Saginata or Mediocanellata (Fig. 95).—This, the beef tape-worm, is the common tape-worm of the United States. Its length sometimes exceeds twenty-five feet. The middle segments measure about one-fourth by one-half inch. The scolex is about the size of a pin-head, and is surrounded by four sucking discs, but has no hooklets (Fig. 96). The uterus extends along the middle line of the segment and gives off about twenty branches upon each side (Fig. 100). The larval stage is passed in the muscles of various animals, especially cattle, where it lies encysted (cysticercus stage).

The larva is ingested with the meat, its capsule is dissolved by the digestive juices, and it attaches itself to the intestinal wall by means of its suckers. It then develops into the mature worm.

The ova are present in the stools of infected persons, often in great numbers. They are spheric or ovoid, yellow in color, and have a thick, radially striated shell (Fig. 101). Their greatest diameter is 30 to 40 µ (about four or five times the diameter of a red blood-corpuscle). Vegetable cells, which are generally present in the feces, are often mistaken for them.

(2) Tænia solium, the pork tape-worm is very rare in this country. It is usually much shorter than Tænia saginata. The scolex is surrounded by four sucking discs, and has a projection, or rostellum, with a double row of horny hooklets (Fig. 97). The uterus has only seven to ten branches (Fig. 100).

The ova closely resemble those of Tænia saginata, but are a little smaller (Fig. 101).

(3) Bothriocephalus latus, the fish tape-worm, is the largest parasite of man, sometimes reaching fifty feet in length, although generally not more than half so long. It is common in some countries of Europe and in Japan, but is very rare in this country. The head is not unlike the bowl of a spoon in shape. It is unprovided with either suckers or hooklets, but has two longitudinal grooves which serve the same purpose (Fig. 98). The uterus, which is situated in the center of the segment, is roset-shaped (Fig. 100).

The larval stage is found in fish, especially the pike.

The ova are characteristic. They measure about 45 by 70 µ, are brown in color, and are filled with small spherules. The shell is thin, and has a small hinged lid at one end (Fig. 99).

Bothriocephalus latus is interesting clinically because it often causes a very severe grade of anemia.

(4) Tænia Echinococcus.—The mature form of this tape-worm inhabits the intestine of the dog and wolf. The larvæ develop in cattle and sheep ordinarily, but are sometimes found in man, where they give rise to echinococcus or "hydatid" disease. The condition is unusual in America, but is common in Iceland and Australia.

The adult parasite is 2.5 to 5 mm. long, and consists of only four segments (Fig. 102). It contains many ova. When the ova reach the digestive tract of man, the embryos are set free and find their way to the liver, lung, or other organ, where they develop into cysts, thus losing their identity. Other cysts, called "daughter cysts," are formed within these. The cyst-wall is made up of two layers, from the inner of which develop larvæ which are identical with the head, or scolex, of the mature parasite. These are ovoid structures about 0.3 mm. long. Each has four lateral suckers and a rostellum surmounted by a double circular row of horny hooklets. The rostellum with its hooklets is frequently invaginated into the body.

Diagnosis of echinococcus disease depends upon detection of scolices, free hooklets, or particles of cyst-wall, which is characteristically laminated and usually has curled edges. These can be found in fluid withdrawn from the cysts, or, less frequently, in the sputum or the urine when the disease involves the lung or kidney (Figs. 55 and 103).

The cyst-fluid is clear, between 1.002 and 1.010 in specific gravity, and contains a notable amount of sodium chlorid, but no albumin.

2. Nematoda.—(1) Ascaris Lumbricoides.—The female is 20 to 40 cm. long and about 6 mm. thick; the male, a little more than half as large. Their color is reddish or brown. They are the common "round-worms" so frequently found in children. Their habitat is the small intestine. Large numbers are sometimes present.

The diagnosis is made by detection of the worms or ova in the feces. The latter are generally numerous. They are elliptic, measuring about 50 by 70 µ, and have an unsegmented protoplasm (Fig. 105). The shell is thick, and is surrounded by an uneven gelatinous envelop which is often stained with bile.

(2) Oxyuris Vermicularis.—This is the "thread-worm" or "pin-worm" which inhabits the colon and rectum, especially of young children. Its presence should be suspected in all unexplained cases of pruritus ani. The female is about 1 cm. long; the male, about 0.6 cm. (Fig. 106).

The worms are not infrequently found in the feces; the ova, rarely. The latter are best found by scraping the skin at the margins of the anus, where they are deposited by the female. They are asymmetrically oval, about 50 µ in length, and often contain a partially developed embryo.

(3) Filaria Sanguinis Hominis.—A description of this worm will be found in the chapter upon the Blood, p. 194. The embryos are sometimes found in urine and chylous fluids from the serous cavities. Their motion is then usually less active than when in blood. That shown in Fig. 107 was alive sixty hours after removal of the fluid. Embryos were present in the blood of the same patient.

(4) Trichina (Trichinella) Spiralis.—This is a very small worm, not exceeding 3 mm. in length when fully developed. Infection in man occurs from ingestion of insufficiently cooked pork, which contains encysted embryos. These reach maturity in the small intestine. The female produces great numbers of young, which migrate to the voluntary muscles, chiefly near the tendinous extremities, and there become encysted.

Trichiniasis is generally accompanied by a marked eosinophilia. The diagnosis is made by teasing out upon a slide a bit of muscle, obtained preferably from the outer head of the gastrocnemius, the insertion of the deltoid, or the lower portion of the biceps. The coiled embryos can easily be seen with a two-thirds objective (Fig. 108).

(5) Uncinaria.—The two varieties of this worm, Uncinaria duodenalis and Uncinaria Americana, are among the more harmful of the animal parasites. They inhabit the small intestine, usually in great numbers, and commonly produce a severe and often fatal anemia. Infection is common in subtropical regions, notably in Egypt, in some European countries, and, especially, in Porto Rico and the West Indies, where about 90 per cent. of the rural population is infected. It is much more common in the United States than was formerly supposed.

The adult worms are seldom found in the feces, but may appear after a dose of thymol followed by a brisk purge. They resemble Oxyuris vermicularis to the naked eye. Ova are usually present in enormous numbers. Those of Uncinaria duodenalis measure about 30 by 50 µ; of Uncinaria Americana, somewhat more. They have a thin, smooth, transparent shell, and their protoplasm is divided into 2, 4, 8, or more rounded segments (Fig. 110).

(6) Strongyloides Intestinalis.—Infection with this worm is by no means so rare in this country as the few clinical reports would indicate. It is very common in subtropical countries, notably in Italy and in southern China. It seems probable that the parasite is the cause of "Cochin China diarrhea," although some authorities regard it as harmless.

The adult worm, which reproduces by parthenogenesis, is about 2 mm. long. It inhabits the upper portion of the small intestine, but neither it nor the ova appear in the stool unless an active diarrhea exists. Ordinarily the eggs hatch in the intestine, and when infection is severe, embryos can be found in the feces in large numbers. These are the "rhabditiform embryos," which measure about 0.40 by 0.02 mm. They are actively motile, and are best found by making a small depression in the fecal mass, filling it with water, and standing in a warm place (preferably an incubator) for twelve to twenty-four hours. The embryos will collect in the water, and can be easily found with a two-thirds objective.

Outside the body the rhabditiform embryos develop into a free-living, sexually differentiated generation. The young of this generation are the more slender "filariform embryos" (Fig. 111). Infection can occur either through these embryos of the free-living generation, or by direct transformation of rhabditiform into filariform embryos and these into the parthenogenic parasitic adult.

(7) Trichocephalus Dispar (T. Trichiurus).—This, the "whip-worm," is 4 or 5 cm. long. Its anterior portion is slender and thread-like, while the posterior portion is thicker (Fig. 112). It is widely distributed geographically, and is one of the most common of intestinal parasites in this country. It lives in the large intestine, especially the cecum, with its slender extremity embedded in the mucous membrane. Whip-worms do not, as a rule, produce any symptoms, although gastro-intestinal disturbances, nervous symptoms, and anemia have been ascribed to them. They, as well as many other intestinal parasites, are probably an important factor in etiology of appendicitis, typhoid fever, and other intestinal infections. The damage which they do to the mucous membrane favors bacterial invasion.

The number present is usually small. The worms themselves are rarely found in the feces. The ova, which are not often abundant, are easily recognized. They are brown, ovoid in shape, about 50 µ long, and have a button-like projection at each end (Fig. 101).