14 
serum, altlioiigli quite narrow, are, however, as wide as we would 
expect. 
Five pregnant rats were inoculated, with a view to finding whether 
their young would acquire an immunity l3y p>lacental transmission. 
Although the mothers bore a very heavy infection, we could never 
demonstrate any parasites in the fetuses nor did the young show any 
evidences of an increased resistance to subsequent infection. Laveran 
and Mesnil mention one immune rat which had two litters; the first 
litter was immune, the second susceptible. In this connection we 
may mention that no case of x^lacental transmission of malaria has 
been reported in which the possibility of postnatal infection has been 
excluded. 
SUSCEPTIBILITY OF ANIMALS TO TRYPANOSOMA LEWISI. 
The wild rat and the sewer rat are the only animals in which there 
is a si3ontaneous conveyance to each other. The white and spotted 
rats are susceptible by inoculation only. Young rats are more sus- 
ceptible than old ones. Rabinowitsch and Kempner report the fail- 
ure to infect pregnant rats. 4Y e inoculated five pregnant females, 
and all bore heaw infections. Xo one has found that the white 
rats harbored trypanosomes spontaneously in their blood. Xo mves- 
tigators have succeeded in infecting other animals with rat trypano- 
somes excei3t Laveran and Mesnil, who infected guinea pigs. We 
tried in vain to infect guinea pigs, rabbits, white mice, cats, a dog, 
a goat, and a horse by intraperitoneal inoculation. In one guinea 
pig we found six parasites in the blood twenty-four hours after 
inoculation, but subsequent examinations of the blood showed an 
absence of all parasites, so that this can not be considered a case 
of infection. Laveran and Mesnil, after intraperitoneal injection of 
a guinea pig with 1 c. c. of blood rich in trypanosomes^ found multi- 
plication forms in the peritoneum two to five days after injection. 
They had numerous failures in bringing about a blood infection, but 
some guinea pigs showed parasites in the blood in the proportions of 
1 : 20 and 1 : 50 of the red blood corpuscles. The infection was of short 
duration. 
When attempting to infect the various animals other than rats we 
injected large amounts of heavily infected rat blood. In some cases 
we injected a rat’s entire blood. White rats and wild rats are so 
susceptible that only one to three droj)s of infected blood, mixed 
with a little sterile salt solution or bouillon and injected intraperito- 
neally, will cause a marked infection. 
AUTO-AGGLUTINATION. 
W e have brought forward the use of this term to signify the agglu- 
tination of a rat’s own trypanosomes while still circulating in his own 
blood. If daily examinations are made of the blood of an infected rat. 
