MICHIGAN ACADEMY OF SCIENCE. 
29 
The trypanosomes, after being* ingested with the blood, slowly adapt 
themselves to the new environment in the gut, and, in a certain per- 
centage of the flies, eventually multiply and become quite numerous. 
A period of incubation of from 2 to 3 weeks is necessary to bring about 
this adaption, and it is an interesting fact, that about this same length 
of time is necessary to secure the first generation of a culture in a 
test-tube. It would seem therefore, that, as in the case of the bird 
trypanosomes, the insect carrier is essentially a culture tube. While 
recognizing this fact, it should be clearly pointed out that it is not fully 
established as to just how the parasite leaves the infected fly to reach 
the wound caused by the bite. 
Recent studies go to show that the cause of sleeping sickness (Tr. 
gombiense ) is represented by several distinct strains. Thus, the West 
African form seems to be more easily destroyed by treatment than is 
the parasite found in Uganda. Another strain has already received a 
distinctive name (Tr. rhodesiense ) . The existence of such strains or 
varieties is not surprising for variations, more or less marked, must be 
expected. We know of such strains in the case of other animal try- 
panosomes and they have been recognized for some time among the 
spirochetes, to say nothing of the bacteria proper. An entirely different 
species of human trypanosome ( ScMzo trypamim Cruzi ) has been de- 
scribed by Chagas (1909), in Brazil. This disease, however,- has been 
but imperfectly studied and it will be necessary to await confirmation of 
the work. 
LEISH MANIA. 
Closely related to trypanosomes, as regards cultural characteristics, 
is a group of parasites which has received the generic name of Leish- 
mania. Unlike the trypanosomes which freely move about in the blood 
plasma, the Leishmanias are actually intracellular parasites, more especi- 
ally of the white blood corpuscles and of endothelial cells. Contrary to 
the commonly accepted view, these cells instead of devouring and de- 
stroying the invading, organism become the hosts of the parasites. For 
that reason the parasites have been called leucocytozoa or pliagocytozoa. 
To one inclined to search for the origin of organisms it would not be 
difficult to assume that the ancestral form of the trypanosomes and 
Leishmanias were intestinal flagellates of insects which differentiated 
with their adaptation to the vertebrate host. The former becoming the 
large typical plasma parasites; while the latter, unable to establish 
themselves in the plasma, were ingested by the leucocytes where in a 
modified form they were able to live and slowly multiply. 
The interest aroused by the discovery of ihe human trypanosome led 
Leishman (1903) to publish an observation made two years before re- 
garding the presence of peculiar rounded bodies in the organs of a 
soldier invalided from his station near Calcutta. The fact that these 
bodies showed a nucleus and a micro-nucleus, and therefore resembled 
rounded or degenerated trypanosomes led him to believe that flagellates 
of this type would be found in fresh blood, or in the fluid obtained by 
splenic puncture during life. 
An examination of such fresh material in Madras failed to demon- 
strate trypanosomes but did show the presence intra vitam of the bodies 
observed by Leishman., The disease in which this organism is found 
