TRYPANOSOMIASIS EXPEDITION TO THE CONGO 9 
either during life or post-mortem from patients admitted to hospital as cases of sleeping 
sickness and from cases of trypanosomiasis. Living trypanosomes in eleven instances 
were seen in the material inoculated. In seven of these the material inoculated was 
from cases of ' sleeping sickness,' in tour from cases of simple trypanosomiasis. Of 
the former, three became infected ; of the latter, two. None of the rats inoculated 
with material taken post-mortem, in which no living trypanosomes were seen, have ever 
become infected. 
Four white mice were inoculated with cerebro-spinal fluid taken from two cases 
of sleeping sickness. Trypanosomes had been found in both cerebro-spinal fluid and 
blood of the first case, in the second trypanosomes were never seen. Two mice were 
inoculated with fluid containing many trypanosomes from the first case. One has 
become infected. Neither of the mice inoculated from the second case has ever shown 
parasites. 
Two rabbits were inoculated with blood containing trypanosomes. The blood 
for one experiment came from a case of sleeping sickness, for the other from a case 
of simple trypanosomiasis. Neither animal has become infected. Four guinea-pigs 
were inoculated with blood containing trypanosomes, two from a case of sleeping 
sickness, and two from a case of trypanosomiasis. Both of the latter have become 
infected. 
The very slight susceptibility of laboratory animals to infection with the 
trypanosomes found in man in the Congo, the great chronicity of the infection produced 
when inoculation has been successful, and the periodicity with which the parasite has 
appeared in the peripheral blood of the experimental animals, are points which greatly 
resemble the animal reactions of Trypanosoma gambiense. 6 The number of experiments 
done is not yet sufficiently large to permit the mention of incubation periods. During 
the eight or nine weeks which the infected animals have been under observation none 
of them have ever shown any gross sign of disease. 
Conclusions 
The examination of trypanosomes seen in stained specimens of blood from cases 
of trypanosomiasis, from cases of sleeping sickness (typical or doubtful), in the specimens 
of cerebro-spinal fluid of the latter cases, and in the blood of experimental animals, 
infected with either of three above-mentioned fluids, has led us to the following 
conclusions . — 
1. The trypanosomes seen in the blood of man, whether symptoms of sleeping 
sickness were present or not, have always been the same. The number of cases in 
which trypanosomes from the spinal fluid have been examined is at present too small 
to permit of a definite description of morphologic characteristics. We have seen forms 
in the cerebro-spinal fluid similiar to those described by Bruce' and Castellani, 4 ' 5 and 
also longer forms similar to those seen in the finger blood of the same cases, 
c 
