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THE HERTER LECTURES. 
II. TRYPANOSOMIASIS. 
LECTURE DELIVERED ON THE HERTER FOUNDATION, JOHNS 
HOPKINS UNIVERSITY, BALTIMORE, MARYLAND, U. S.A. 
9 OCTOBER, 1912. 
By GEORGE H. F. NUTTALL, M.A., M.D., Ph.D., Sc.D., F.R.S., 
Fellow of Magdalene College; Quick Professor of Biology, Cambridge. 
The term trypanosomiasis is applied to-day to a group of diseases 
affecting vertebrates and caused by parasitic Protozoa belonging to the 
family Trypanosomidae. These parasites occur chiefly in the blood 
plasma and the typical form possesses an elongated body, an undulating 
membrane, a single nucleus, a blepharoplast, and a chromatic filament 
running along its length from near the blepharoplast, along the margin 
of the undulating membrane, to terminate freely at one end of the body. 
The latter has a somewhat spiral form, the protoplasm being alveolar 
and at times showing a granular structure. An axial filament has 
been described as occurring in some forms. One species. Trypanosoma 
equvperdum, occurs largely in the lymph, and another, T. gambiense, 
may invade the cerebrospinal fluid. They are actively motile organisms, 
multiplying usually by longitudinal or multiple division. Numerous 
species of trypanosomes have been successfully cultivated in vitro in 
the presence of haemoglobin, and by this means many trypanosomes 
have been discovered in animals in which these parasites occur in such 
scanty numbers that their presence cannot be detected microscopically. 
Thus, a large percentage of birds and cattle in different parts of the 
world have been found to harbour trypanosomes in their blood. 
It would appear from the evidence gathered of late years that the 
majority of these parasites are conveyed from host to host by 
blood-sucking ectoparasites, either arthropods or leeches, whereas in 
some cases there is clear proof (partly experimental) that infection may 
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