On the relation of the parasitic protozoa to each other and to human disease / by E.J. McWeeney.

  • McWeeney, Edmond Joseph, 1864-
Date:
1905
Catalogue details

Licence: In copyright

Credit: On the relation of the parasitic protozoa to each other and to human disease / by E.J. McWeeney. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    according to him, old females (macrogametes) [ ? macroga- metocytes]. After a time these “sink” to the level of schizonts; in other words, produce a brood without having been fertilised. This mode of reproduction—the skipping of the sexual generation—appears to me to be homologous with the phenomenon amongst ferns, first described by De Bary under the name of “ apogamy.” The bokinet which is to form the “ male” Trypanosomes, is distinguished ah initio by its small size, large nucleus and absence of reserve material in its protoplasm (Fig. 2.) By a process of reduction it gets rid of one half of its nucleus— the half which is preserved in the female—and the re- mainder splits up so as to form eight minute Trypanosomes. These he regards as microgametes which, however, are unable to perform their physiological function of fertilisa- tion. This act is only performed at one period of the life- Fig. 2.—Trypanosoma (Halteridmm) noctiws. Development of “male” Trypanosomes from the Ookinet (after Schaudinn); c, d, gradual disappearance of larger half of nucleus, whilst from the smaller half the microgametes are developed (e and /). history of the parasite, viz., within a few minutes of its arrival within the stomach of the mosquito. As the result of these processes, the intestinal canal of the mosquito becomes inundated with “ Trypanosomes ” of all three kinds. Sometimes they are produced in such swarms that their resting-stages occupy all the epithelium, and the mosquito dies of the disease. Ordinarily, the insect feeds three times, and it is during these three periods of digestion that the parasites make their way down the bowel, through the wall of the colon, and so into the blood- stream, whereby some get carried to the ovaries, where they infect the young brood; most, however, are carried to the front of the body-cavity into the head, where they accumulate round the pharynx, and ultimately rupture into it, and so obtain access to the lumen of the proboscis. The