20 
the peritoneal fluid in addition to the blood their number did not ^ 
reach a point beyond the number obtained by snbcntateons injection. 
3. By intrasfomachal injection . — We have read some discussion 
bearing on the natural mode of infection with trypanosomes in which 
infection followed the eating of a trypanosome rat by a healthy one. It 
was held that this could not be considered a case of intrastomachal in- > 
fection because the possibility of the entrance of the parasites thi’ough 
wounds about the mouth, lips, or teeth had not been excluded. 
TT e therefore arranged a series of experiments in which we thought 
all likelihood of infection through wounds was removed and that 
infection occurred through the stomach. Twelve white rats were 
chloroformed sufficiently to prevent any struggling. Then a small- 
sized catheter well oiled was passed into the stomach without , 
encountering any resistance; injection of trypanosomes was made 
through the catheter, and the rats were then placed in separate cages 
and examined daily for parasites in the tail blood. Eleven out of the 
12 developed blood infections fullv as heavv as was obtained bv anv 
other form of inoculation. The time which elax^sed before their 
appearance in the blood was as follows: Two in four days, one in flve 
davs, three in six davs, three in seven davs, and two in ei 2 :ht da vs. 
TTe see that infection is considerablv delaved bv this method, the i 
c t. c 7 
earliest being in four davs and the latest in eight davs. 
Jf. Transmission hy feeding . — The success of the intrastomachal 
injections naturally lead to a series of experiments to determine 
whether infection would not occur by feeding when all precautions 
were taken to x^revent any wounding about the teeth or mouth. ; 
Seven white rats, apparently free from mouth wounds, were x^^^t 
mto separate cages to x^revent fighting, and they were fed with soft j 
food, so that no wounds would result from the gnawing of bones. j 
They were each given a single feeding with the entme blood of a | 
trypanosome rat. Xo other part of the infected rats was given to 
them. Trypanosomes appeared in the tail blood in five of the seven 
at x^eriods of time which averaged six days. 
TTild rats were then subjected to similar feeding experiments. In 
the blood of five wild rats we found parasites after three, seven, eight, 
nine, and ten days. Some of the rats had enormous numbers in their 
blood, while others had comparatively few. 
TT e conclude from these experiments that infection may take place 
thi’ough the digestive tract and that the spread of the disease among 
wild rats may be due to feeding ux^on one another, esx^ecially since , 
the instinct of fighting and x^luck is so well implanted in them and is 
brought into action on slight x^rovocation. TTe found it necessary to 
separate the wild rats in our stock cage to prevent losses from injuries j 
inflicted on the weaker ones by the stronger. 
After beginning the feeding experiments we were surprised to read 
the results obtained by Rabinowitsch and Kemx)ner. They made intra- 
stomachal injections through a stomach tube in four rats, but were | 
