G. H. F. Nuttall 
279 
giving an exhaustive list, I would mention that, in addition to the 
animals already noted, the chimpanzee, macacus, lemur, cat, pig, goat, 
sheep, hedgehog, mouse, rat, guinea-pig, rabbit, horse and donkey have 
been found susceptible to infection with T. gamhiense. On the other 
hand, birds, reptiles and amphibia appear to be immune. The parasite 
has been conveyed experimentally to susceptible animals either by flies 
captured in a wild state or by clean flies purposely infected in the 
laboratory. Monkeys, sheep, goats and the duikerbok have been 
successfully infected in this manner. 
Experiments carried out with G. palpalis in captivity have shown 
that but a limited number—-about 5 to 6 "/o—become infective after 
feeding upon blood containing T. gamhiense. It is worthy of note, in 
this connection, that Ross and Milne have shown that T. rhodesiense 
exhibits periodicity in respect to numbers in the blood. Miss Muriel 
Robertson has just reported what appear to be negative periods in 
monkeys suffering from trypanosomiasis. Although trypanosomes can 
be found in their circulation they do not appear to have reached a stage 
in their development when they are capable of infecting Glossina. She 
reports, moreover, that a greater proportion (up to 21 “/o) of G. palpalis 
become infected if the flies are starved for several days after imbibing 
trypanosomatous blood. In such dies a certain number of trypanosomes 
always degenerate and die but others soon begin to multiply rapidly 
throughout the gut, and this multiplication has been seen to continue 
within the dy’s gut up to the 95th day, being maintained by repeatedly 
feeding the dy upon clean blood. The trypanosomes disappear from 
the dy’s proboscis very soon after the insect has partaken of infected 
blood. The parasites occur in a variety of forms within the gut, they 
have not been found in the coelomic cavity, and it is only after a period 
of 25 to 28 days following the infective meal that they appear in 
the salivary glands of the insect. During the few hours immediately 
following an infective meal, the dy may transmit the trypanosome, this 
being doubtless due to parasites ejected from the proboscis before it has 
become cleaned. Then follows a period of 25-28 days during which the 
dy is incapable of producing infection. It is only when the parasites 
appear in the salivary gland that the insect becomes infective. The 
parasites in these glands resemble T. gamhiense as seen in mammalian 
blood and they persist in the glands as long as the dy lives. Experiments 
made by inoculating the contents of dies into susceptible animals at 
various periods after an infective meal have given concordant results 
with those just mentioned. When the gut contents of a dy are injected 
