The Animal Parasites of Man. Max Braun
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Название: The Animal Parasites of Man
Автор: Max Braun
Издательство: Bookwire
Жанр: Медицина
isbn: 4057664648037
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Entamœba williamsi, E. bütschlii, E. hartmanni and E. poleki (Prowazek) are probably only varieties of E. coli.
Fig. 4.—So-called autogamy of Entamœba coli. A, rounded amœba; B, nucleus dividing; C, the two daughter-nuclei giving off chromidia; D, each nucleus has formed two reduction nuclei; E, cyst membrane formed, and gamete nuclei are dividing; F, cyst with two synkarya.
The principal feature distinguishing Entamœba coli from E. histolytica is the formation of eight-nucleate cysts by the former as contrasted with the tetra-nucleate cysts of the latter. The cyst-wall of E. coli is thicker than that of E. histolytica (tetragena). Further, E. coli does not usually ingest red blood corpuscles, nor are “chromidial blocks” present inside its cyst (see p. 40).
According to Chatton and Lalung-Bonnaire14 (1912) the entamœbæ of vertebrates should be placed in a separate genus Löschia, as they differ in their life-history from E. blattæ, the type species of Entamœba. Leidy (1879), however, named the genus Endamœba, but further researches are necessary on biological variation among these organisms.
Entamœba histolytica, Schaudinn, 1903.
Syn.: Amœba coli, autt. p. p. Amœba dysenteriæ, autt. p. p.
The average size of the amœboid trophozoite is 25 µ to 30 µ. In fæces diluted with salt solution the amœbæ swell to 40 µ and more. There is sometimes separation of the body substance into a strongly refractile vitreous ectoplasm and a corneous endoplasm, pronounced even in repose, although the former is not equally thick at all parts of the periphery. In the endoplasm generally there are numerous foreign bodies (bacteria, epithelial cells, colourless and red blood corpuscles (fig. 6), and occasionally living flagellates of the intestine). The nucleus is 4 µ to 6 µ in diameter, and may be difficult to recognize because it is sometimes weakly refractile and poor in chromatin. Its shape is slightly variable; it is usually excentric, sometimes wholly peripheral at the limit of the two parts of the body. Vacuoles are not present in quite fresh specimens, but appear later. In the study of E. histolytica, the morphological characters of the trophozoite or vegetative stage of the organism formerly separated as E. tetragena (figs. 5, 6, 8a) must be considered (see p. 38).
Fig. 5.—Entamœba histolytica (tetragena form), showing three successive changes of form due to movement. × 1100. (After Hartmann.)
The history of the development of these species, which give rise to amœbic enteritis as distinguished from bacillary dysentery, was formerly not so well known as that of E. coli. Upon being introduced into cats (per anum) dysenteric amœbæ provoke symptoms similar to those in man. In the latter, besides metastatic liver abscesses, abscesses of the lungs, and, according to Kartulis, cerebral abscesses are occasionally produced. Marchoux (1899) states that when the disease has lasted for some time liver abscesses are produced in cats also.
Fig. 6.—Entamœba histolytica which has ingested many red blood corpuscles. × 1100. (After Hartmann.)
Fig. 7.—Section through wall of large intestine (of a man) close under an ulcer caused by Entamœba histolytica. A, amœbæ that have penetrated partly in blood-vessels (Bv), partly in tissue of submucosa to the muscularis. Magnified. (After Harris.)
In the large intestine of infected cats the amœbæ creep over the epithelium, and here and there they force the epithelial cells apart, as well as removing them or pushing them in front of them; the amœbæ thus insert themselves into the narrowest fissures. They penetrate also into the glands through the epithelium, and thence into the connective tissue of the mucosa. Intestinal and glandular epithelia perish under the influence of these parasites: the cells are pushed aside, fall to pieces or are absorbed by the amœbæ. In the connective tissue of the mucosa the amœbæ migrate further, and often accumulate above the muscles. Finally they rupture this and force their way into the submucosa. In cats, apparently, the penetration is not so great as in men, according to Kruse and Pasquale. During their migration the parasites also gain access to the lymph-follicles of the wall of the intestine, which become swollen and commence to suppurate; follicular abscesses arise and after their rupture follicular ulcers. The diseased patches in the mucosa are markedly hyperæmic and numerous hæmorrhages are set up. Roos and Harris state that the amœbæ also penetrate into the blood-vessels (fig. 7) and this explains the occurrence of metastatic abscesses.15 The whole submucosa is severely swollen at the diseased spot and undergoes small-celled infiltration in the neighbourhood of the colonies of amœbæ. From these findings Jürgens (1902) draws the conclusion16 which is followed here, that the amœbæ are causative agents of the enteritis of cats, which disease is well defined, both pathologically and anatomically. Subsequent researches confirm the experience of earlier authors; great precautions were taken to exclude errors, hence, as with Gross and Harris, no exception can be taken to their results. The inoculation material was derived from soldiers who suffered from amœbic enteritis in China and who were admitted into the garrison hospital at Berlin. In order to be independent of the patients themselves, transmission experiments from cat to cat were performed, after the first experiments on cats yielded positive results. This was also effected by rectal feeding as employed by earlier workers. Such appeared necessary in order to prevent the evacuation of the inoculation material per anum, as well as to avoid the employment of morphia and ether narcosis. Forty-six cats were used for the experiments. Ten cats received tested stools containing motile amœbæ from soldiers suffering from amœbic enteritis contracted in China. Sixteen other cats received stools from cats infected by inoculation. All the animals sickened and suffered from the disease. Five cats received dejecta from human amœbic enteritis in which, however, no motile amœbæ were present. Thirteen cats received stools from soldiers who suffered from bacillary dysentery. None of the latter cats took the complaint and none showed changes in the large intestine upon sectioning. The injection of various bacteria, obtained from a stool of amœbic enteritis pathogenic to cats, remained without result in both the cats employed for this experiment. Lastly, two cats, which had been kept with those artificially infected, were taken ill spontaneously and suffered from the disease. In the opinion of Harris, who ascertained the harmless nature of bacteria derived from the intestinal flora containing dysenteric amœbæ, young dogs are capable of being infected.
Within the large intestine an active increase of Entamœba histolytica must occur. Nevertheless, Jürgens did not definitely find changes that might be interpreted in this sense. Schaudinn (1903) observed division and gemmation in vivo. Both processes, in which the nucleus divides by amitosis, can only be distinguished by the fact that the daughter individuals are similar in binary fission but dissimilar in gemmation, whether they make their appearance singly or in greater numbers. Schizogony, resulting in the formation of eight individuals, which is so characteristic for Entamœba coli, was not observed. (But schizogony, into four merozoites, is now known to occur. Gemmation processes are apparently degenerative.)
Resistant stages, which serve for transmission to other hosts, are according СКАЧАТЬ