There is a karyosome in each nucleus. Other bodies of unknown function, and possibly composed of chromatin, occur on or near the axostyles.
Fig. 19.—Lamblia intestinalis. A, ventral view; B, side view; N, one of the two nuclei; ax., axostyles; fl1, fl2, fl3, fl4, the four pairs of flagella; s, sucker-like depressed area on the ventral surface; x, bodies of unknown function. (After Wenyon.)
Division has not been observed in the flagellate stages of the Lamblia, but it occurs within the cysts. The resistant cysts (fig. 20, e) are oval and are surrounded by a fairly thick, hyaline cyst wall. They measure 10 µ to 15 µ by 7 µ to 9 µ, and may be tetranucleate. According to Schaudinn, the cysts arise from the conjugation of two individuals, and nuclear rearrangement occurs.
L. intestinalis occurs in its flagellate stage in the duodenum and jejunum, and rarely as such in the other parts of the intestine. Normally it is found in the large intestine as cysts, which are voided with the fæces. The hosts of Lamblia include Mus musculus, M. rattus, M. decumanus, M. silvestris, Arvicola arvensis and A. amphibius, the dog and cat, rabbit, sheep and man. Cysts voided with the fæces of infected animals reach plants or drinking water, and thence are transferred to man.
The flagellate in these different hosts exhibits some variation in size and in the problematic chromatic bodies. Bensen has suggested the species L. intestinalis from man, L. muris from the mouse and L. cuniculi from the rabbit. It is not certain whether these different species are necessary, as the variation may be due to differences of environment.
Fig. 20.—Lamblia intestinalis. a, from the surface; b, from the side; c, on intestinal epithelium cells; d, dead and e, encysted. (After Grassi and Schewiakoff.)
Like Trichomonas, Lamblia can multiply under inflammatory conditions of the alimentary tract. Thus they are found in cases of diarrhœa, carcinoma of the stomach, etc. The parasites attach themselves by their sucking discs to the epithelial cells of the gut (fig. 20, c), and though their numbers may be very great, their direct pathological significance is not fully known. Their occurrence in cases of diarrhœa has been explained as being due to the increased peristalsis, which has detached the parasites from the epithelium. Free flagellate forms perish in stools if kept, more especially if the temperature falls below 0° C. or rises above 40° C. Lamblia has often been found in dysenteric diseases, especially in the East, and is said to be the causal agent of certain diarrhœas in India. Mathis (1914)45 found Lamblia in cases of diarrhœa with dysenteriform stools in Tonkin. He also discovered healthy carriers of Lamblia cysts.
The parasite under discussion was first observed by Lambl (1859) in the mucous evacuations of children. He regarded the parasite as a Cercomonad and termed it Cercomonas intestinalis, which name as a rule is applied to Cercomonas hominis, Davaine, although Stein had already pointed out the difference between the two species. Grassi (1879) observed this species first in mice (calling it Dimorphus muris), and subsequently in human beings in Upper Italy and named it Megastoma entericum. Bütschli and Blanchard then laid stress on the identity of this species with Lambl’s C. intestinalis (1859), and consequently called it Megastoma intestinale. Later, Blanchard drew attention to the circumstance that the generic name Megastoma chosen by Grassi had already been used four times for various kinds of animals, and established the genus Lamblia. Accordingly, L. intestinalis is the valid name, and should be generally adopted.
In Upper Italy the parasite in the encysted condition has also been seen by Perroncito in man. At the same time, Grassi and Schewiakoff began a new investigation of specimens from mice and rats. In Germany, L. intestinalis was found by Moritz and Hölzl, Roos, Schuberg and Salomon. Moritz and Hölzl confirmed the relative frequency of the species. In Königsberg, Prussia, a student found encysted Lamblia in his fæces. One case was reported from Finland by Sievers, another case from Scandinavia by Müller. Frshezjesski and Ucke reported cases from Russia. Jaksch announced the occurrence of the parasite in Austria; Piccardi mentioned their presence again in Italy. They were reported from Egypt by Kruse and Pasquale, and from North America (Baltimore) by Stiles. Noc stated that 50 per cent. of the population of Tonkin harboured Lamblia. Finally, the structure of L. intestinalis has been described by Metzner (1901), and by Wenyon46 (1907) in mice.
In all these cases L. intestinalis has been observed in the small intestine, or in the evacuations of patients with intestinal diseases. It has also been found in the intestine of healthy subjects. Just as Trichomonas intestinalis may be found inhabiting the stomach in diseases of that organ, in which an alkaline reaction is present (carcinoma), so has L. intestinalis been found to occur under similar circumstances (Cohnheim, Zabel). However, in Schmidt’s case, 1 per cent. hydrochloric acid was certainly stated to be present. Infection takes place by the ingestion of cysts (fig. 20, e), as was established by Grassi, experimentally on himself. Cereal food-stuffs, contaminated with Lamblia cysts from vermin of the locality, such as rats and mice, serve to convey the infection to man. Such cysts may probably be found in street-dust, etc. Stiles induced infection in guinea-pigs, and Perroncito in mice and rabbits, by means of cysts of Lamblia from human beings. Stiles suspected that flies could transport Lamblia cysts. Mathis (1914) found that L. intestinalis was not amenable to emetine, at any rate in its cystic stage.
Order. Protomonadina, Blochmann.
The smallness of the Protomonadines and their less superficial situation than the Polymastigines, may be the cause that so far as the species occurring in man are concerned, they were formerly less well known. As regards parasitic species, this group may be divided as follows, according to the number of flagella and the presence or absence of an undulating membrane:—
(1) Cercomonadidæ, with one flagellum at the anterior extremity, without an undulating membrane.
(2) Bodonidæ, with two flagella, without an undulating membrane, except in Trypanoplasma.
(3) Trypanosomidæ, with one flagellum, and an undulating membrane along the length of the body in some genera.
Family. Cercomonadidæ, Kent emend. Bütschli.
Small uniflagellate forms, without cytostome.
Genus. Cercomonas, Dujardin emend. Bütschli.
Oval or rounded organisms, with the aflagellar end often drawn out into a tail-like process.
Cercomonas hominis, Davaine, 1854.
Davaine found flagellates in the dejecta of cholera patients. They had pear-shaped bodies, lengthening to a point posteriorly. Their length was from 10 µ to 12 µ, and a flagellum about twice as long as the body projected from one extremity (fig. 21). A nucleus was hardly recognizable. Occasionally a somewhat long structure (cytostome?) appeared at the anterior extremity. The animals moved with remarkable activity. They also attached themselves by means of their posterior extremities and swung about around the point of attachment. Davaine found a smaller variety, only about 8 µ long, in the dejecta of a typhoid patient (fig. 21, b).
Fig. 21.—Cercomonas hominis, Dav. a, larger, b, smaller variety. Enlarged. (After Davaine.)
Fig. 22.—Cercomonas