TRYPANOSOMES, TRYPANOSOMIASIS, AND SLEEPING SICKNESS 85 
II. EXAMINATION OF ORGANS OF ANIMALS INFECTED WITH 
TRYPANOSOMA GAMBIENSE 
We examined the organs of a large number of animals such as monkeys, dogs 
(including puppies), rabbits, guinea-pigs, rats, and mice, who had succumbed to 
infection, with various strains of T. gambiense. 
The brains of some of the monkeys in which the infection had run a longer 
course showed a marked congestion of the vessels, both in the meninges and in the 
brain itself. Some brains, especially those in which the infection had run a rapid 
course, were very anaemic. Those of the latter group showed little or no micro- 
scopical changes ; those of the former groups, however, presented marked changes 
affecting the vessels. 
The section of one of the chimpanzees' brains showed extreme congestion, 
especially in the basal ganglia. Fig. 9 is a section from the optic thalamus of this 
brain. It shows a vessel with a large perivascular space distended with red blood 
corpuscles and among them a fair number of leucocytes. The endothelium is a little 
proliferated. The same changes were also observable in many of the neighbouring 
vessels. The meninges did not show any changes. The pons, medulla, and spinal 
cord were normal. A Rhesus monkey presented, in the region of the left central 
gyrus, a haemorrhagic cicatrix. Its surface was depressed below the level of the 
surrounding brain, and was of a vellowish colour. Microscopically it showed 
destruction of the brain tissue, with much pigmentation at the bottom of the softening. 
Two of the infected baboons microscopically examined showed congestion of the 
vessels of the brain and spinal cord. Microscopically there were haemorrhages around 
the vessels of the grey matter of the brain, a good number of lymphocytes being 
present among the red cells. The grey matter of the spinal cord showed many 
localized haemorrhages. A few of the Rhesus monkeys, dying after infection of long 
duration, showed perivascular changes of varying extent in the brain and spinal cord. 
Those cases which showed perivascular changes also showed changes in their nerve 
cells similar to those in the human cases. The processes of the cells were often broken 
away. Sometimes no nucleus was to be found, and the protoplasm appeared vacuolic. 
In the more chronic cases of trypanosomiasis in dogs, rabbits, and guinea- 
pigs, haemorrhages were present in the grey matter of brain and cord in a limited 
number. The vessels also often contained a large number of white blood corpuscles, and 
leucocytes were also found in the haemorrhages. The meninges showed nothing 
abnormal except a few small haemorrhages. Animals dying more rapidly from the 
infection did not show these changes in the central nervous system. The other 
