The Animal Parasites of Man. Max Braun

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СКАЧАТЬ 1.—Myxosporidia. The spores have valvular coats, with or without caudal appendages, with two, rarely four, polar capsules. They live free in such organs as the gall or urinary bladder, but are chiefly found in connective tissue. They occur especially in fishes.

      Order 2.—Microsporidia. Spores with coats or sporocysts; no caudal appendage, with one polar capsule. They usually live in the tissues of Arthropoda.

      Order 3.—Sarcosporidia. Elongate parasites of the muscular fibres of amniotic vertebrates, on rare occasions they occur also in the connective tissue; the spores, which are kidney or sickle-shaped, are naked and apparently have no obvious polar capsule.

      Order 4.—Haplosporidia. Simple organisms, forming simple spores; they occur in Rotifers, Polychætes, Fish and Man.

      Class IV.—Infusoria (Ciliata). The body is generally uniform in shape, with cilia and contractile vacuole, frequently also with cytostome; usually has macro- and micro-nucleus; live free in water and also parasitically.

      The orders Holotricha, Heterotricha, Oligotricha, Hypotricha and Peritricha are classified according to the arrangement of the cilia.

      Class V.—Suctoria. Bodies with suctorial tubes, contractile vacuoles, macro- and micro-nucleus, no cytostome. They generally invade aquatic animals as cavity parasites, yet also attack plants; early stage ciliated. Live sometimes as parasites on Infusoria. [The Suctoria are frequently regarded as a sub-class of the Infusoria.]

      The Protozoa and Protophyta are sometimes united under the term Protista (Haeckel, 1866). The Spirochætes are Protists (see pp. 114–128).

      Class I. SARCODINA, Bütschli, 1882. Order. Amœbina, Ehrenberg. A. Human Intestinal Amœbæ.

      The first record of the occurrence of amœba-like organisms in the human intestine, that is, in intestinal evacuations, was that of Lambl (1859); nevertheless, the case was not quite conclusive, as the occurrence of testaceous amœbæ of fresh water (Arcella, Difflugia) was also reported. In 1870 Lewis found amœbæ associated with disorders of the large intestine in patients in Calcutta. A year later Cunningham reported from the same locality that he had observed on eighteen occasions, in one hundred examinations of dejecta from cholera patients, colourless bodies with amœboid movements, which became encysted and multiplied by fission. The daughter forms were said to be capable of dividing again, but they might also remain in contact. Contractile vacuoles were not noticed. The same bodies were observed also in simple diarrhœa (twenty-eight cases out of one hundred.)

      Fig. 1.—Amœba coli, Lösch, in the intestinal mucus. (After Lösch.)

      The case reported by Lösch in 1875 attracted more attention. It was that of a peasant, aged 24, who came from the province of Archangel. He was admitted into Eichwald’s clinic at Petrograd with symptoms of dysentery. In the discharges containing blood and pus, Lösch found amœbæ in large numbers. When at rest these amœbæ measured from 20 µ to 35 µ; in a state of movement their length might extend up to 60 µ (fig. 1). The pseudopodia appeared only singly, and, since they were hyaline (ectoplasmic), were thus distinguished from the markedly granular endoplasm that enclosed a spherical nucleus of from 5 µ to 7 µ in diameter. One or more non-contractile vacuoles were present. Quinine enemata had the effect of making the amœbæ disappear from the fæces and thus causing the diarrhœa to abate. Four months after admission the patient died from the results of intercurrent pneumonia. At the autopsy ulceration of the large intestine was found, especially in the lower parts. Lösch connected the amœbæ with the ulcerations by experiments made on four dogs by injecting them with recently passed stools (per os et anum). Eight days after the last injection numerous amœbæ were found in the fæces of one of these dogs; eighteen days after the injection the animal was killed. The mucosa of the rectum was inflamed, covered with blood-stained mucus and ulcerated in three places. Numbers of amœbæ were found both in the pus of the ulcers and in the mucus. The three other dogs remained healthy. From these observations Lösch concluded that the species of amœba described by him as Amœba coli could not be regarded as the primary cause of the disease, but that it was certainly capable of increasing a lesion of the large intestine already present, or at least of preventing its healing.

      B. Grassi (1879) found in the stools of healthy as well as in those of diarrhœic patients from various localities in Northern Italy, amœbæ similar to those discovered by Lösch. As this was of frequent occurrence, the pathogenicity could not be definitely established. Normand, formerly naval surgeon at Hong-Kong, observed numerous amœbæ in the dejecta of two patients suffering from colitis.

Many further investigations, which cannot be quoted in detail, showed not only that intestinal amœbæ were widely distributed in man, but indicated with greater certainty their rôle as agents of dysentery. The Commission sent out by the German Government in the year 1883 to investigate cholera in India and Egypt—whose members discovered the cholera bacillus—also collected information with regard to dysentery. In five cases of dysentery examined post mortem at Alexandria, with the exception of one case in which ulceration of the colon had already cicatrized or was approaching cicatrization, R. Koch found amœbæ as well as bacteria in sections from the base of the ulcers, although such had previously escaped notice in examination of the dejecta. Encouraged by these results, Kartulis (1885), who had discovered amœba-like bodies in the stools of patients suffering from intestinal complaints at Alexandria, continued his investigations. The results, obtained from more than 500 cases, gave rise to the theory that typical dysentery was caused by amœbæ as were also the liver-abscesses that often accompany it. Kartulis supported his theory not only by the regular occurrence of amœbæ in the stools of dysenteric patients and their absence in other diseases, and by the occurrence of the parasites in ulcers of the large intestine and in the pus from liver-abscesses, but also by experiments which he performed on cats. These were infected by injection per anum of stool material rich in amœbæ from subjects of dysentery. The infection took place also when amœba-containing, but bacteria-free, pus from liver-abscesses was used. It has been objected that the infection of man with Amœba coli, as the dysenteric amœbæ were then generally designated, does not take place per anum but per os. This difficulty, however, diminished in proportion as the encysted states of amœbæ (fig. 2), long known in the case of other Protozoa, became understood. The infection of man (Calandruccio, 1890) and of cats (Quincke and Roos) succeeded solely when material containing such stages was used. Amœbæ introduced into the intestine multiply there by fission (Harris, 1894). However, this theory, to which various other authors gave support on the grounds of their own observations, encountered opposition. Thus it was established that amœbæ were not found in patients in every place where dysentery was endemic, or else they were much rarer than was expected. Further, amœbæ were present in the most varied kinds of intestinal diseases, both of infective and non-infective characters. Also they were present in quite healthy persons.

      Moreover, for various reasons, infection experiments on animals failed to supply proof, and finally a bacterium was discovered (Shiga, 1898) to be the excitant of one form of dysentery. Agglutination attested the specific part played by this organism, as it was produced by the blood serum of a person suffering from or recovered from dysentery, but not by the serum of one who was uninfected. Bacillary dysentery consequently was a distinct entity. The final step to be taken was to decide whether there was a specific amœbic enteritis (amœbic dysentery or amœbiasis, according to Musgrave).

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