222 Dr. H. B. Fantham. History of T. gambiense [Oct. 15, 
The latent bodies, which are the post-flagellate stages of one generation of 
trypanosomes, become the pre-flagellate stages of the succeeding generation 
of trypanosomes. Such pre-flagellate, Crithidia-like parasites in various 
stages of metamorphosis may be seen in the peripheral blood of the host 
(figs. 32, 34 to £2), when the parasites are increasing 1n numbers therein. 
A basal granule (blepharoplast of Minchin) is seen at the base of the 
flagellum of some stained flagellating parasites (fig. 37). 
It may be added that in dealing with an isolated case of an intermediate 
stage of a parasite between the flagellate and the rounded body, it is some- 
times difficult to determine whether the given stage is pre-flagellate or post- 
flagellate, that is, whether the given parasite is proceeding in development 
towards the flagellate stage or away from it towards the rounded body. 
The Significance of the Non-flagellate or Latent Forms of Trypanosomes. 
Inoculation with Latent Bodies produces Trypanosomiasis, 
R. Ross and D. Thomson (1910) report periodic variation in the 
numbers of the trypanosomes found in the blood of a patient W. A., suffering 
from Rhodesian Sleeping Sickness. Fantham and J. G. Thomson (1910) 
report similar periodic variation in the number of the parasites in the 
peripheral blood of sub-inoculated animals (rats, guinea-pigs, and rabbits). 
During the periods of decrease of the parasites in the peripheral blood, I find 
that latent (non-flagellate) bodies are present in relatively large numbers in 
the internal organs of the host. The latent bodies are formed at or near the 
period of maximum increase of the trypanosomes in the peripheral blood. 
The latent bodies are especially numerous in the spleen and bone marrow on 
the downward slope of the curve representing the numbers of the parasites 
in the peripheral blood of the host. Change of the latent forms into 
trypanosomes takes place on the rise or upward slope of the curve. 
There is, of course, a mutual action and reaction of the host and the 
parasite, the resistance of the host probably being greatest when the flagellate 
trypanosomes within it are beginning to decrease, thus helping to bring 
about the assumption of the rounded form by many of the flagellates, 
so that latent or resistant non-flagellate stages of the parasite are then 
numerous. 
The occurrence of latent bodies also helps to explain the successful inocula- 
tion of animals with trypanosomiasis when no flagellates can be found in the 
blood inoculated from a previously infected animal. Although it might be 
urged that flagellate trypanosomes, in numbers too few to recognise, may 
actually be present in the infected blood inoculated, yet it is possible to 
inoculate only latent, non-flagellate bodies, and give the inoculated animal 
