H. E. Durham 
233 
that small additions of serum of normal blood have some sheltering 
or delaying action. Normal cat or dog serum has a greater delaying 
effect than normal rabbit serum, but it was found that the serum of 
rabbits in the highly cachectic condition of the later stages of nagana 
had a still greater effect, von Dungern attributes variation in this 
response to haemolysis to the amount of lecithin substances in the 
case of normal animals; such may also be the cause in nagana. 
Summary. 
1. Some cases of remarkable resistance to nagana infection are 
recorded. 
2. Although such birds as pigeons are unable to harbour the 
trypanosoma brucei, the kestrel is able to do so. 
3. Attention is drawn to certain changes which are brought about 
by the trypanosome infection and the need for more precise chemical 
investigation of these haematozoal diseases. 
Notes on blood parasites observed in Christmas Island (Straits 
Settlements) and in the Malay Peninsula. 
Christmas Island possesses quite a number of peculiar species in its 
fauna, and it is regrettable that observations were not made before 
animals had been imported to this isolated station, as well as that 
my own notes are so incomplete. 
Rats. There are three species of rat (1) the large Mus nativitatis 
had already become rare about the settlement at the time of my visits 
and I was unable to obtain either a freshly killed or a living specimen 
although a reward was offered. 
(2) Mus macleari. A number of these rats was obtained and 
examined, of these nine were collected about the settlement; all were 
males and two of them had abundant trypanosomes in their blood. The 
trypanosome appeared morphologically like the T. lewisi of English 
rats. 
Two other M. macleari were caught on the top of Phosphate Hill, 
some three or four miles from the settlement, one was a male the other a 
female aud both were free from infection. Another was taken about 
half way up the hill and showed abundant trypanosomes in its blood; 
