. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. COURSE OF SLEEPING SICKNESS 103 Under such circumstances they have a tendency to mass together in large numbers, up to a hundred or more, hke sheep in a storm, all with their flagellated ends projecting from a common center (Fig. 23). Such " primary agglomerations " may adhere to form " secondary agglomerations " comprising altogether many hun- dreds of parasites. When the unfavorable conditions disappear, the trypanosomes disentangle themselves without any apparent ill effects, alth
. Animal parasites and human disease. Medical parasitology; Insects as carriers of disease. COURSE OF SLEEPING SICKNESS 103 Under such circumstances they have a tendency to mass together in large numbers, up to a hundred or more, hke sheep in a storm, all with their flagellated ends projecting from a common center (Fig. 23). Such " primary agglomerations " may adhere to form " secondary agglomerations " comprising altogether many hun- dreds of parasites. When the unfavorable conditions disappear, the trypanosomes disentangle themselves without any apparent ill effects, although a few of them remaining agglutinated may die and disintegrate. Another peculiar habit described by some investigators is the extrusion from their bodies of very minute granules, really tiny buds from the nucleus, which ultimately develop into new trypanosomes. This is said to occur just be- fore the temporary disappearance of the trypanosomes from the blood. The Disease. — The course of the disease caused by trypano- some infection is insidious and irregular in the extreme. The Gambian and Rhodesian diseases are essentially ahke in their symptoms and in the course they run, except that the latter is usually more rapid in development and more virulent in effect, as a rule causing death within three or four months after in- fection. The variety of the Gambian disease found in Nigeria is comparatively mild and of long duration. The bite of an infected tsetse fly is usually followed by itching and irritation near the wound. After a few days fever is felt and a peculiar tenderness of the muscles develops, so that strik- ing against an object causes undue pain. Usually the fever comes and goes at irregular in- tervals of days or weeks or even Fig. 24. Negro infected with trypano- months, an infected person f™*^'f'™/"'?'-^''^''^'-^'f'^1^°^^- ' _ ^ (Alter Kolle and Wassermann.) sometimes carrying the para- sites in his blood, as shown by its infectivity when injected i
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