230 
Haematozoa 
On 16. vi. 99 nearly the whole of the blood (about 5 c.c.) of a highly 
infected rat was injected subcutaneously as before into the breast of the 
kestrel. On the next day a few active trypanosomes together with 
clumped masses of dark crinkled rat red corpuscles, leucocytes and 
granular matter were seen in a sample removed. A rat inoculated with 
this sample died in ten days of nagana. The bird was again examined 
locally three days after the injection, no trace of haematozoa or of rat 
blood corpuscles could be found ; leucocytes however were abundant. 
Two rats inoculated died in 12 and 17 days of typical nagana. 
On 30. VI. a rat was inoculated with negative results. 
The kestrel remained in apparently good health. Owing to its 
fractious nature and the danger of injuring it, its temperature was not 
taken regularly, one day it was noted to be 4T7° C.; this is in accordance 
with the well known high temperature of birds. 
In order to control this experiment with the kestrel, a pigeon was 
treated in exactly the same manner and contemporaneously. The dose 
given amounted to nearly 10 c.c. of citrated rat’s blood (there were 
2,500,000 trypanosomes per cubic millimetre in the undiluted blood). 
Rats were inoculated on each of the four following days ; only one 
of these died, death being within 48 hours apparently due to sepsis. 
On 10. XI. 98 or 59 days after the first injection, a second inoculation 
of highly infective rat’s blood was given. Rats were inoculated at 
various periods, all with negative result. The temperature record of 
the pigeon was rather higher than that of the kestrel, viz. 42'5° C. 
Until actual observations have been made on birds of prey in nagana 
infested regions, it is only possible to say that they might conceivably 
be carriers of infection. Koch’s observation that Glossina will feed on 
crocodiles is of interest in this connexion. 
Remarks on the Pathogenic Action of Trypanosoma hrucei 
If the course of the disease as it occurs in rats is compared with 
that which obtains in the rabbit, it is clear that the trypanosomal form 
of the parasite, as such in the circulating blood, has but a small share in 
the determination of illness. Thus a rat may have several hundred 
thousand trypanosomes in each cubic millimetre of its circulating blood, 
without showing grave signs of its rapidly approaching death. The 
same is true of guinea-pigs, for I have watched a buck which was most 
zealous in its attentions to a doe, a few minutes after counting 500,000 
trypanosomes per cubic millimetre in its blood; moreover the animal’s 
