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The following experiments indicate once more that animals 
inoculated in the laboratory with T rypanosoma gambiense may recover 
from the consequent infection. The connection between these and the 
preceding observations is evident. Their bearing on the question 
whether human trypanosomiasis is invariably fatal is most important. 
I. A brown stallion was inoculated in the Senegambia (6) from a case of 
human trypanosomiasis. For the earlier history consult Memoir X\ I (7) of this 
School. In October, 1905, the animal appeared to be quite healthy; no enlarge¬ 
ment of the glands was present, and no trypanosomes could be found in the blood. 
Its temperature was always normal. Sub-inoculations from it were made as follows: 
November 1.2, 1906. A guinea-pig was inoculated subcutaneously with ijc.cm. 
of almost pure blood. It was accidentally killed on the 31st of December. 
Trypanosomes were never seen. On the same date a rat was sub-inoculated with 
ioc.cm. Trypanosomes were never seen at any time. The rat died on l ebniary4. 
1907, from acute enteritis. 
January 16, 1907. A guinea-pig and two rats were inoculated with 20, 17 and 
20 c. cm. of pure blood respectively. The guinea-pig and the first rat are still 
alive and have never become infected. The second rat died on the nth of 
February from an extensive skin disease. 
This series of experiments pointed to the fact that the pony had entirely 
recovered from the infection by Trypanosoma gambiense. On January 21st it was 
re-inoculated subcutaneously with 7 c. cm. of citrated, infected blood, showing one 
try'panosome to one to five fields, from a guinea-pig infected with Trypanosoma 
gambiense. This, however, had no effect. The temperature has been taken twice 
daily for the past year ; there has been no rise, even after the inoculation. The 
animal remained in good health ; retained its appetite and did not lose weight. The 
pony was most carefully examined day by day, but trypanosomes were never seen. 
On March 15 two rats were sub-inoculated, receiving 30 and 250.011. 
respectively of almost pure blood. Up to date they have not become infected. On 
March 20 the pony was again inoculated intraperitoneally with 25c.cn!. of infected 
gambiense blood showing numerous trypanosomes. For a few days afterwards there 
was slight auto-agglutination of the cells, but trypanosomes have never been seen. 
As in the first instance, no rise of temperature or other morbid symptoms have been 
noticed. The experiments are still in progress. 
II. A donkey was inoculated in 1904 (7). Since the fall of 1905, the animal 
has been in perfect health. No enlargement of the glands, or trvpanosomes, have 
e\er been noticed. On January 16, 1907, a guinea-pig (20 c.cm. pure bloodl and a 
rat (20c. cm.) were sub-inoculated, but up to date have not become infected. On 
January 21 the donkey was inoculated subcutaneously with 7 c.cm. of blood from 
a guinea-pig infected with T. gambiense. No rise in temperature or other symptom 
followed. For a few days the red cells showed auto-agglutination, but trypano¬ 
somes were never seen. On March 15 two rats were sub-inoculated from the 
donkey with 35 c.cm. of pure blood each. Doth are still alive and have not become 
infected. On March 20 the donkey was re-inoculated intraperitoneally with 25 c.cm. 
of blood containing T. gambiense (one per field), but without result. No symptom? 
of any sort are apparent. The donkey is still under observation. 
III. 1 he cow inoculated by Thomas and Dreinl (7) was under observation 
until June, 1906, when the animal passed out of our hands. It was in good health 
all the time. No trypanosomes were seen and the glands were not enlarged. 
