The Sarcosporidia are always enveloped in a membrane, which is probably formed at an early stage. In a few cases it remains thin and simple, in other cases a radially striated ectoplasmic layer is present (figs. 104, 108), which has been variously described. From the inner integument, which may be homogeneous or fibrous, thick or thin, membranes or trabeculæ pass into the interior of the body, forming anastomosing partitions, and so producing a system of chambers of various sizes that do not communicate with one another (figs. 104, 108). These chambers are occupied by sickle- or bean-shaped bodies (spores or sporozoites), or various developmental stages of them. The oldest spores are found in the centre of the Miescher’s tubes or trophozoites. If they are not liberated they die there, so that the central chambers of the tube are empty and hollow.

In the youngest Sarcosporidia (40 µ in length) from the muscles of the sheep there occur, according to Bertram, small roundish or oval cells (4 µ to 5 µ), the nuclei of which are half their size, and are embedded in a granular protoplasmic mass. In somewhat larger, and therefore older, cylinders, the investing membrane of which already shows both layers, the cells have become larger (to 7 µ) and are more sharply outlined from each other (fig. 106). These uninucleate cells may be considered as pansporoblasts. In each pansporoblast division of the nucleus occurs (fig. 107), and meanwhile the pansporoblasts become isolated within the chambers, the dividing partitions of which originate from the granular protoplasm which is present between the pansporoblasts. The numerous uninucleate daughter forms produced within the chambers become spores direct (fig. 108).

The process commences in the centre of the cylinders or sarcocysts, and then progresses towards the extremities, the parasites meanwhile increasing in size, and new pansporoblasts being continually formed at the extremities (fig. 107).

The spores (sometimes called Rainey’s corpuscles), vary in shape according to the species, but are also of different form individually. They are mostly kidney-, bean- or sickle-shaped (fig. 109), and of small size, sometimes reaching 14 µ by 3 µ to 5 µ. They are apparently surrounded by a thin membrane, and at one extremity (according to the discovery of L. Pfeiffer, confirmed by van Eecke, Laveran and Mesnil) contain an obliquely striated body (fig. 109) often homologized with the polar capsule, while the greater part of the spore is taken up by the nucleate sporozoite. Several authors state that they have also observed filamentous appendages (polar filaments) at one end of the spores, and have seen two kinds of spores in the same Sarcosporidium. Spores of various species of Sarcosporidia may contain metachromatic granules, often centrally placed (fig. 109). These granules may be metabolic or possibly may contain toxin (see below).

Although the natural mode of transmission of the Sarcosporidia remains to be determined, yet various experimental researches on the problem are of interest and importance. Theobald Smith (1901) found that mice could be experimentally infected with S. muris by feeding them with the flesh of other infected mice. The incubation period was a long one, namely forty to fifty days. Thus, on the forty-fifth day after feeding young Sarcosporidia were found, and seventy days after feeding spore formation began. Ripe spores were found two and a half to three months after the commencement of these experiments. This mode of infection—a cannibalistic one—hardly seems likely to be the natural method for the infection of sheep and ruminants generally. Smith’s researches have been confirmed. Nègre225 (1910) found that the fæces of mice fed on infected muscular tissue were infective to other mice when ingested by them. Negri226 infected guinea-pigs with S. muris by feeding them on infected mouse flesh, and found that the parasite in guinea-pigs showed different characters from those exhibited by it in mice. Darling227 also succeeded in infecting guinea-pigs with S. muris, and Erdmann infected mice with S. tenella (from the sheep).

According to Erdmann228 (1910) the Sarcosporidian spore germinates in the intestine of the host, which has recently ingested infected material. The spore liberates its contained toxin—sarcocystin—which acts upon the adjacent intestinal epithelium, whereby the latter is shed, and an amœbula creeps out of the spore. The amœbula is able to penetrate the denuded area and get directly into the lymph-spaces of the submucous coat of the intestine. The first period of development, lasting some twenty-eight to thirty days, is said to be passed in the lymph-spaces of the intestine. Later the amœbula reaches a muscle fibre. Writing in May, 1914, Erdmann229 records the appearance of small amœboid and schizogony forms six days after infection of the host. Crawley230 (1913) controverts some of these statements and considers that the Sarcosporidian spore, still sickle-shaped, bores its way into the epithelial cells of the intestine and comes to rest there. The spore then becomes round or elliptical, and peripheral masses of chromatin appear within it, suggesting schizogony. This happens about twelve hours after feeding, and in twenty-four hours the spores appear to have left the intestine. More recently (May, 1914), Crawley231 considers that there is sexual differentiation among the Sarcosporidian spores, a few hours after their ingestion by the host.

Interesting discussions have occurred as to the site of the toxic sarcocystin within the spore. Metachromatic granules occur in the middle of the Sarcosporidian spore (fig. 109), and the toxin may be contained in these grains, as they disappear, according to Erdmann, before the amœbula penetrates the denuded intestinal wall. However, a polar capsule, containing a polar filament, may be present at one end of a Sarcosporidian spore. Laveran and Mesnil described a striated area at the more pointed end of the spore of S. tenella, which area they consider to represent a polar capsule. Fantham232 (1913) found a vacuole-like, polar capsule area in the spores of S. colii from the African mouse-bird. The sarcocystin may be contained in the polar capsule. The nucleus of the spore is generally at the opposite, blunter end.

Again, various authors have stated that Sarcosporidian spores may occur in the blood of the host at times. If so, then an intermediate host may be concerned in their transmission. Perrin suggested that Sarcosporidia might be spread by blow-flies and flesh-flies.

The classification of the Sarcosporidia as proposed by R. Blanchard, which was based on their various habitats, can no longer hold, because the same species may occur in the muscles as well as in the connective tissue. For the present, the few species that are known may be placed in one genus, Sarcocystis, Ray Lankester, 1882.

The following species of Sarcocystis are of interest:—
S. miescheriana, Kühn, 1865, in the pig.
S. bertrami, Doflein, 1901, in the horse.
S. tenella, Railliet, 1886, in sheep. S. tenella bubali in buffaloes in Ceylon and Egypt.
S. blanchardi, Doflein, 1901, in cattle.
S. muris, Blanchard, 1885, in the mouse, to which it is lethal.
S. hueti, Blanchard, 1885, in the seal.
S. colii, Fantham, 1913, in the African mouse-bird, Colius erythromelon.

Also various Sarcosporidia from antelopes, monkeys, opossum, birds, the gecko and wall-lizard are known.

The spores of S. muris, S. bertrami, S. tenella, and S. colii can multiply by longitudinal fission.

Sarcosporidia observed in Man.

(1) Lindemann233 found on the valves and in the myocardium of a person who had died of dropsy certain brownish masses, 3 mm. in length and 1·5 mm. in breadth which he regarded as gregarines. If these were actually independent animal organisms it may be suggested that they were Sarcosporidia. Rivolta (1878) named the species S. lindemanni.

(2) Rosenberg234 found a cyst 5 mm. in length and 2 mm. in breadth in a papillary muscle of the mitral valve of a woman, aged 40, who had died from pleuritis and endocarditis. The cyst contained no scolex nor hooklets of tænia. Numerous small refracting bodies, round, oval or kidney-shaped, were found in a daughter cyst, as well as sickle-shaped bodies. The description hardly appears to indicate Sarcosporidia.

(3) Kartulis235 observed Miescher’s cylinders of various sizes in the liver (?) and in the muscular system, of a Sudanese who had succumbed to multiple abscesses of the liver and abdominal muscles. This may be considered as the first actual case of the occurrence of Sarcosporidia in man. Koch in 1887 described a case in Egypt.

(4) The case reported by Baraban and St. Remy236 was at once demonstrated as certain. It related to a man who had been executed, and in the laryngeal muscles of whom Sarcosporidia were found; the length of the parasites varied between 150 µ and 1,600 µ, their breadth between 77 µ and 168 µ. The affected muscular fibres were distended to four times their normal thickness. This species was described by Blanchard as “Miescheria” muris, but according to Vuillemin, it was more probably Sarcocystis tenella of the sheep.

(5) Vuillemin has also described a case of Sarcosporidia found in the muscles of a man who died from tubercle at Nancy. The author considered that the parasite corresponded to S. tenella.

(6) Darling237 (1909) found Sarcosporidia in the biceps of a negro from Barbados.

The Myxosporidia, Microsporidia, Actinomyxidia and possibly the Sarcosporidia may be included within the section Cnidosporidia (Doflein), since they possess spores containing polar capsules.

Order. Haplosporidia, Caullery and Mesnil.

Rhinosporidium kinealyi, parasitic in man, must now be considered in greater detail. This organism was found in nasal polypus in India, and has since been recorded from the ear as small nodules in the external auditory meatus. The Indian cases came from the neighbourhoods of Calcutta and Madras, and the parasite has been seen in Ceylon. Similar structures have since been described from the United States and South America.

The Rhinosporidium polypus is said not to be particularly painful, though nasal forms must interfere with breathing to some extent. The first nasal polyp reported from India formed a vascular pedunculated growth on the septum nasi and was about the size of a large pea or raspberry. It was compared with a raspberry, being red in colour with a number of small whitish dots upon its surface. When the tumour was cut, a number of similar whitish dots were seen within. These were the cysts of Rhinosporidium. According to Minchin and Fantham240 (1905), they vary considerably in size and measure up to 200 µ or 250 µ in diameter. Each possesses a cyst wall which varies in thickness in different cysts. Its outer wall is always firm and distinct, the inner limit being less definite at times. Each large cyst is filled with numbers of spherical or oval bodies, showing every gradation between small ones at the periphery and large ones at the centre (fig. 112). Roughly, three zones of parasites can be distinguished in a large cyst, a peripheral set consisting of the youngest parasites, an intermediate group and a central, oldest zone. A large cyst may possess a pore for the egress of its contents. Some of the cysts show polar distribution of the zones.

The youngest forms of Rhinosporidium are difficult to detect. They are small, granular masses, round, ovoid or irregular and at times even amœboid in appearance. These are young trophozoites. They increase in size, but encystment occurs early, the outer layer becoming firm so that the organisms have a definite contour. Each is soon multinucleate and the cytoplasm segments around the nuclei. The cyst thus becomes full of uninucleate pansporoblasts or sporonts, with a peripheral layer of undifferentiated protoplasm. The pansporoblasts grow in size. In the larger cysts the formation of pansporoblasts progresses at the expense of the peripheral layer of protoplasm, which, however, continues to grow, so that the cyst as a whole increases in size. The pansporoblasts at first are uninucleate (fig. 112, a), and then undergo nuclear multiplication. This is well seen in the intermediate zone of parasites, where the pansporoblasts show first one, then two, then four or more spores (fig. 112, b), while in the oldest centrally placed pansporoblasts, about a dozen or sixteen closely packed spores (fig. 112, c), can be seen. The spore is small and rounded, and its nucleus is clear and distinct. The fully formed pansporoblast or spore morula becomes surrounded by a membrane.

Certain of the cysts have been found in a ruptured condition, whereby the spores have been liberated into the surrounding tissue. It is almost certain that the spores serve for the auto-infection of the host, for though the tumours of Rhinosporidium seemed to have been removed entirely, it has been found that they recur, some minute fragment of the parasite having probably been left behind. The method whereby the parasite reaches new hosts has not yet been determined, and it would be of interest if its life-history could be more fully investigated.

The Asiatic specimens of R. kinealyi were first described in detail by Minchin and Fantham (1905) from material briefly reported to the Laryngological Society of London in 1903, by O’Kinealy. Material obtained by Dr. Nair, of Madras, was described by Beattie241 in 1906. This material came from Cochin. Castellani and Chalmers have found similar polypi in Ceylon.

Wright242 has described the parasite from Memphis, Tennessee. Seeber243 in 1896 described nasal polypi in Buenos Ayres, and in 1900 Wernicke named the parasite therein Coccidium seeberi. Seeber’s parasite is a Rhinosporidium, R. seeberi, and may ultimately be found to be the same as R. kinealyi. Ingram244 reports Rhinosporidium cysts, with pores in the cyst walls, in conjunctival polypus and in papilloma of the penis in India. Zschokke has reported the presence of Rhinosporidium in horses in South Africa.

Class IV. INFUSORIA, Ledermüller, 1763.

The Infusoria (or Heterokaryota, Hickson, or Ciliophora, Doflein) include the Ciliata and the Suctoria. A few authorities, including Braun, raise the Suctoria (or Acinetaria) to separate rank as a class, but this is not widely followed.

The body of the Ciliata usually is bilaterally symmetrical and is enveloped in a cuticle which has numerous openings for the protrusion of the cilia. Most kinds have a fixed shape, whilst changes in the form of others are brought about by the contractions of the body substance. The latter exhibits hyaline ectoplasm, in which myonemes, and occasionally also trichocysts (minute spindle-shaped bodies) appear, and granular endoplasm which may contain numerous vacuoles. The cilia, on whose various arrangements the classification is based, are always processes of the ectoplasm. Their form varies; they may be hair-like, or more rarely thorn-like, spur-like, or hook-shaped; undulatory membranes also may occur, which are probably composed of fused cilia.

With the exception of some of the parasitic species, an oral cavity, peristome or cytostome, is always present. It is frequently beset with cilia or provided with undulatory membranes, which help to waft the food inwards; sometimes there is an anal aperture (cytopyge) generally placed at the opposite pole of the organism. A cytopharynx fringed with cilia or sometimes with a specialized supporting apparatus is connected with the peristome. Vacuoles form round the ingested food, and in many species a constant rotation goes on in the endoplasm. Often one, and sometimes two contractile vacuoles are present, the frequency of the pulsations of which depends on the surrounding temperature. Sometimes special conducting channels lead to the vacuoles, or there are outlet channels leading to the exterior.

There is in almost every case a large nucleus (macronucleus), and lying close up to it a small nucleus (micronucleus). The form of the large nucleus varies according to the species. Numerous nuclei are not very common, but these occur in Opalina, which lives in the hind-gut of amphibia, and is also distinguished by the absence of an oral aperture.

Reproduction is effected by binary fission; less commonly, after encystment, by multiple division, or by budding. The divisions can be repeated many times, but finally cease, and then the conjugation of two specimens brings about a regeneration, particularly of the nuclei. Numerous examinations (Bütschli, Hertwig, Maupas, Calkins) have demonstrated that after two individuals have associated by homologous parts of the body, the micronucleus separates from the macronucleus, becomes larger and divides twice by mitosis, so that four micronuclei are present in each one of the two individuals forming the couple. Three of these nuclei perish and become absorbed, the fourth gradually passes to the portion of protoplasm connecting the two conjugants, which has originated by absorption of the cuticle at the point of contact of the conjugants. After a further division one micronucleus of each conjugant passes over into the other conjugant, and fusion ensues between the two micronuclei of each individual. Complicated changes and divisions may occur, but only the main principles can be noted here. A new nuclear body is thus formed in each conjugant, and soon divides into two. Of the segments thus produced one becomes a micronucleus, and one or several of the others, as the case may be, form or amalgamate into a new macronucleus, the old macronucleus usually perishing or becoming absorbed during the conjugation. Usually, sooner or later, the two conjugants separate, or may have separated already, and again multiply independently by fission until a series of divisions by simple fission is again followed by conjugation. The theoretical significance of conjugation cannot be dealt with fully here. It may be remarked, however, that the macronucleus plays no part in it, but governs entirely the metabolism of the Infusorian, whereas the micronucleus is essentially a generative nucleus from which macro- and micro-nuclei are again and again produced.

Encystment amongst the Infusoria is very general, and is essentially a means of protection when the surrounding medium dries up. Doubtless these cysts are frequently carried long distances by the wind, which explains the wide geographical distribution of most species. Also, multiplication often takes place in the encysted condition.

Some Infusoria live a free life, others are sedentary; the latter form colonies in fresh as well as in salt water. Numerous species are parasites of various lower and higher animals,245 and a few also are parasitic in man.

The Prague zoologist, v. Stein, introduced a classification of the Infusoria that has been almost universally adopted. It is founded on the different position of the cilia on the body. Though, no doubt, artificial, it is a convenient system. Bütschli has compiled a better one.246 But for our purpose Stein’s system is sufficient:—

The Infusoria observed in man belong to the order Heterotricha, with few exceptions.

Genus. Balantidium, Claparède et Lachmann.

The body is oval, 60 µ to 100 µ in length (up to 200 µ according to Janowski), and 50 µ to 70 µ in breadth. The peristome is funnel-shaped or contracted, the anterior end being then broadened or pointed according to the degree of contraction (figs. 113, 114). The ecto- and endo-plasm are distinct, the latter is granular, containing drops of fat and mucus, granules of starch, bacteria, and occasionally also red and white blood corpuscles. There are usually two contractile vacuoles, seldom more. The anus (cytopyge) opens at the posterior extremity. The macronucleus is bean- or kidney-shaped, rarely oval; the micronucleus is spherical.

Balantidium coli lives in the large intestine of man, in the rectum of the domestic pig, and has been found in monkeys. It propagates by transverse division, but conjugation and encystment are known to take place.247 Transmission to other hosts is effected by the cysts of the parasite (fig. 114).

Balantidium coli, first seen by Leeuwenhoek, was described by Malmsten in 1857 in a man aged 35 years, who had two years previously suffered from cholera, and since then had been subject to diarrhœa. The examination showed an ulcer in the rectum above the mid sphincter ani, in the sanguineous purulent secretion of which numerous Balantidia were swimming about. Although the ulcer was made to heal, the diarrhœa did not cease and the stools contained numerous Balantidia, the number of which could only be decreased by extensive enemas of hydrochloric acid.

The second case related to a woman who was suffering from severe colitis, and who died ten days after admission. The malodorous, watery evacuations contained innumerable Balantidia, in addition to pus, and at the autopsy the anterior portion of the large intestine was found to be infested with them.

Subsequently this parasite has often been observed in human beings, and various cases have been recorded. These occurred in Russia, Scandinavia, Finland, Cochin China, Italy, Germany, Serbia, Sunda Islands, Philippine Islands, China, and in other parts of Asia and in America. Other cases were reported by Askanazy, Ehrnroth, Klimenko, Nagel, Koslowsky, Kossler, Waljeff, Strong and Musgrave, Glaessner248 and others. Sievers found B. coli very common in Finland.

In the majority of the cases described by Sievers from Finland, and in other cases from Central Europe, the patients suffered from obstinate intestinal catarrh, which did not always cease even after the Balantidia had disappeared. On the other hand, Balantidia have occasionally still been found to persist, though in small numbers, after the catarrh has been cured. Some authors, nevertheless, do not regard Balantidia as the primary cause of the various diseases of the large intestine, which often commence with the development of ulcers, but they consider that they may aggravate these diseases and render them obstinate. According to Solowjew, Askanazy, Klimenko and Strong and Musgrave, however, the parasites penetrate the intestinal wall, and give rise to ulcerations which may extend deeply into the submucosa, and even be found in the blood and lymphatic vessels of the intestinal wall. According to Stokvis, B. coli occurs also in the lung; at all events this author states that he found one living and several dead paramæcia (?) in the sputum of a soldier, returned from the Sunda Islands, who was suffering from a pulmonary abscess. Sievers has shown that B. coli might occur in persons not suffering from intestinal complaints, but E. L. Walker249 (1913) states that every person parasitised with B. coli is liable sooner or later to develop balantidian dysentery.

Since Leuckart confirmed the frequent presence of B. coli in the rectum of pigs, and corresponding observations were made in other countries, the pig is universally considered to be the means of the transmission of Balantidium to man. The encysted stages only serve for transmission, because, according to all observations, the free parasites have a very small power of resistance. They perish when the fæces have become cool; they cannot live in ordinary, slimy, or salt water. As they are killed by acids even when much diluted, they cannot pass through the normal stomach alive except under the most unusual circumstances. The pigs, in whose intestines the Balantidium appears to cause little or no disturbance, evacuate numerous encysted Balantidia with the fæces, and their occasional transference to man brings about their colonization there, but perhaps only when a disease of the colon already exists.

Experimental transmission of the free parasites to animals (per os or per anum) yielded negative results, even in the case of pigs. Casagrandi and Barbagallo (1896), however, had positive, as well as negative, results. They employed healthy young cats, or cats in which catarrhal entero-colitis had been artificially induced (which in other experiments is apt to cause the death of the animals experimented upon in about six or seven days), or finally cats that had dilatation of the rectum with alkaline reaction of the fæces. An attempt to infect three healthy cats by injecting human fæces containing Balantidium into the rectum proved negative, in so far as the fæces of the experimental animals had an acid reaction and contained no Balantidia, but at the autopsy performed eight days after infection a few encysted parasites were found in the mucus of the ileum. In the case of four cats suffering from entero-colitis, into which human fæces containing Balantidia were introduced per os, Balantidium cysts were found in the fæces three days after the last ingestion. Great numbers, moreover, were found in the cæcum and the posterior part of the small intestine at the autopsy of the animals, which died about eight days after the commencement of the experiments. Actual colonization, therefore, was not effected in either series of experiments. Free or encysted Balantidia of pigs were used for further experiments. The experiments proved negative when fæces containing cysts were injected into the rectum of healthy cats (three experiments), or cats (two) suffering from spontaneous intestinal catarrh, or when such material was introduced per os into three healthy cats. In the case of two cats with intestinal catarrh artificially produced, a small number of the active Balantidia injected into the rectum remained alive. Larger quantities of fæces containing encysted Balantidia were introduced into two other cats affected with the same complaint. These, certainly, did not appear in the fæces, but small numbers, free and alive, were found in the cæcum. Similarly, encysted Balantidia were introduced into two cats with dilated rectum, and whose fæces had an alkaline reaction. In these cases no parasites appeared in the fæces, but three and five days later, when the two animals were examined, a very small number were discovered free in the large intestine. Klimenko did not succeed in infection experiments with B. coli on young dogs, whose intestines had been artificially affected by disease.

More recent experiments by Brumpt have shown that young sucking pigs can be infected with Balantidium from infected monkeys (Macacus cynomolgus) and suffer heavily from the same, whereas the Balantidium of the pig is rarely harmful to its host. This and previous experiments may be thought to suggest that there are perhaps several pathogenic species, and also that harmless strains of Balantidium may occur. At the same time, it must be remembered that a large proportion of the cases recorded of Balantidian colitis occur among swineherds and butchers, that is, among people in frequent contact with pigs. Morphologically, there are practically no differences between the Balantidia found in man, monkeys and pigs, and it is probable that one species only, under slightly different environmental conditions, may be responsible for the colitis observed. In any case, efficient prophylactic measures should be taken against balantidiasis in countries where it may occur, by confining the pigs and not allowing them to run in yards and dwellings.

E. L. Walker (1913) has given a good summary of work on balantidiasis. His own researches in the Philippines showed that monkeys could be infected by Balantidia both from pigs and men. Parasites may appear in the stools only at infrequent intervals. He believes that the ciliates are the primary etiologic factor in the symptoms and lesions of balantidian dysentery.

Behrenroth (1913) has given an interesting account of Balantidium coli and its pathogenic significance.

Balantidium minutum, Schaudinn, 1899.

Nyctotherus faba, Schaudinn, 1899.

[Nyctotherus] africanus, Castellani, 1905.

In the fæces of a native of Uganda who suffered from sleeping sickness and diarrhœa and had in his intestine Ascaris lumbricoides, Trichocephalus trichiurus and Ancylostoma duodenale, Castellani found a curiously shaped Infusorian, 40 µ to 50 µ long, and 35 µ to 40 µ broad, with spherical macro- and micronucleus and a contractile vacuole (fig. 118). He included the organism in the genus Nyctotherus, perhaps wrongly, or the parasite may have been deformed. After the patient’s death the same parasite was found in the intestine and especially in the cæcum.