On Nagana, or Tsetse Fly Disease. 109 



In many cases an iron reaction has been obtained with the liver, 

 spleen, and kidney (ammonium sulphide ; and K 4 FeCy 6 + HC1). 



VI. Distribution of Hwmatozoa. 

 A. Blood. 



After a latent period of some days, haematozoa are invariably found 

 in the blood at some time or other during the course of the illness. 



1. Itatx. When the animal is inoculated with small quantities of 

 infective blood, the latent period averages 3 4 days. When, however, 

 a large number of haematozoa is inoculated into the peritoneal cavity, 

 the parasites may be found in the blood even after a few hours. 



When the haematozoa have once appeared in the blood, they are 

 generally found therein to the end, gradually increasing in number till 

 the blood literally teems with them. During the early stages of the 

 disease, however, variations are frequently noted, inasmuch as an 

 increase on one day may be followed by a marked decrease on the next. 

 In a few cases they have even temporarily disappeared from the circu- 

 lation for a day or two, but this is distinctly rare in rats and mice, 

 although common in other animals. 



At the later stages the haematozoa may amount to 2,000,000 

 3,000,000 per cubic millimetre. 



2. Mice. What has been said of rats applies also to mice. 



3. Rabbits. In these animals, after inoculations with minute quan- 

 tities of blood, the parasites first appear in the blood in about eight 

 days, about the same time as the pyrexial attack. They remain in the 

 general circulation for a day or two in small numbers ; this is followed 

 by a disappearance and reappearance for a variable number of days at 

 irregular intervals. In the animals which have been systematically 

 examined the haematozoa do not appear abundantly until towards the 

 close of the disease ; the largest number which has been estimated near 

 the time of death has been 60,000 per cubic millimetre (compare rats 

 and mice), but even at that time they may be scanty and difficult to 

 find. They are- also to be found in the fluid of the local oedema and 

 discharge from wounds, conjunctiva, or genitals. Although haematozoa 

 may be so scanty that they cannot be discovered by the microscope 

 (sometimes even after centrifugalising), the animals show marked 

 clinical symptoms. Their blood has often been proved to be infective. 



4. j) g Sm Early in the disease, from 46 days, the haematozoa may 

 be absent from the blood, but observations on their presence during life 

 in the lymphatic glands have not been made. Towards the end they 

 become very numerous (100,000300,000 per cubic millimetre). Varia 

 tions in the number of haematozoa are common, but as a rule haematozoa 

 are numerous throughout the disease. 



5. Cats. The latent period is about five days; then the haematozoa 



