1 85 — 
ior dogs, for the dog sent from this Laboratory to Dr. Laveran 
died on the 3gth day of the disease and two dogs inoculate by 
Dr. Laveran in Paris died after 33 and 38 days respectively. 
Three hundred thirty-six days after inoculation (Jan. 26), the 
guinea pig died. Many motile trypanosomes were found in the 
heart’s blood at autopsy. Heart’s blood was used to inoculate e 
dog and trypanosomes were demonstrated in the peripheral blood 
of this dog 26 days later. The dog was sent :o the Department 
of Agriculture, Washington, D. C., and I hâve been informed 
by Dr. Mohler that trypanosomes could not be demonstrated du- 
ring a period of six months either by blood examination or ani¬ 
mal sub-inoculation. The animal is living niné months after ino¬ 
culation. 
Heart’s blood was also used to inoculate another guinea pig, 
but c.iis guinea pig during seven months showed no évidences of 
the disease. 
Two hundred severity-nine (27g) days after inoculation to déter¬ 
miné whether the virulence of the trypanosomes had diminished 
for mules, a mule was inoculated with this strain and at the same 
time two other mules were inoculated with another strain which 
had been more recentlv recovered from a naturallv infected mule. 
- 
Strain : 
Hoof No. of animal : 
Date of inoculation ; 
Period of incubation : 
Duration of Disease ; 
Strain t>f 
reduced virulence 
121 
nov. 30 1910 
Eleven days 
Recovered 
Strain of 
usual virulence 
382-3-B 
113 
nov. 30 1910 
Eight days 
44 days 
382-3-B 
2G4 
nov. 30 1910 
Eight days 
105 days 
In this experiment the latent period or period of incubation 
was eertainly prolonged in the strain derived from the guinea 
pig that survived 336 days. The three animais were treated in the 
same inanner with arsenic (Holmes’ method), but the only ani¬ 
mal that recovered was the one inoculated with the avirulent 
strain. This mule became emaciated, trvpanosomes were detected 
on many occasions, but in Âpril lie grew fat and appeared in good 
condition; and it was thought that he had been cured by arsenic 
médication. On August 16, however, while examining films, I 
noticed that although the animal’s température had been normal 
for months and trvpanosomes had been absent from films for 
[43 days, bis blood contained auto-hemagglutinins. Suspecting 
that he was still infected, a guinea pig and white rat were inocu- 
