TRYPANOSOMES, TRYPANOSOMIASIS, AND SLEEPING SICKNESS 27 
parasites ; after which the temperature may vary very little from the normal. Loss 
of weight is usually a feature of the disease. Anaemia is present but is not so marked 
as in rabbits infected with T. dimorphon. Paralysis of the posterior limbs has been 
seen in two cases about thirty hours before death. The parasites after the first 
appearance usually continue constantly in the peripheral blood, gradually increasing 
until there may be forty to sixty to a field. These high numbers may continue for 
ten days before the animal dies, or diminution in the number coincident with an 
increase in leucocytes can be noted. 
Periodicity in some cases is a prominent feature, the parasites at times almost 
completely disappearing and remaining so for some days. This feature is observable 
in the more chronic cases. Rupture of the spleen has occurred in seven cases. Five 
of these cases were of the very acute form in which, after the incubation period, a 
continuous and rapid increase of the parasites had been noted. In the remaining two 
cases the disease was more prolonged. One death happened on the ninth day of the 
disease ; numerous parasites were present in the blood, and the animal died suddenly. 
The abdomen contained a large quantity of fluid blood, no lesion of the spleen or 
other organ could be detected, but the peritoneum was studded with small pin-head 
sized haemorrhages. One case of haemorrhagic nephritis conducing to the death of 
the animal occurred. Enlargement of the glands is not marked. If a very attenuated 
parasite be injected infection may not take place ; the animal is not protected by such 
an inoculation. 
Rabbits 
The parasite has gradually become more virulent for these animals. The incu- 
bation period after subcutaneous inoculation is longer than after intraperitoneal or 
intravenous inoculation. An incubation as short as four days and as long as fifteen 
days has occurred. The average after intraperitoneal injection is nine days, after 
intravenous four to seven days. Some animals have died in twenty-six to thirty-five 
days after intravenous inoculation, showing parasites in large numbers in their blood. 
The more chronic form of the disease can last from seventy-eight to one hundred and 
fifty-seven days. 
These animals show a pronounced periodicity, the parasites being often absent 
from their blood for four to nine days at a time, to reappear in small numbers and 
gradually increase to one to ten to a field. Large numbers of trypanosomes to a field, 
as in the guinea-pigs, are rare. In acute cases the number of parasites is somewhat 
increased, and they are almost constantly present. In both the acute and chronic types 
of the disease anaemia is a very marked symptom. Soon after the appearance of the 
parasites in the peripheral blood the anaemia is noted, this rapidly advances, so that 
the blood is of a very pale serous character. At the same time a marked loss of 
weight occurs. In the chronic cases the animals may become mere skin and bones ; 
