1908.| The Life-history of Trypanosoma equiperdum. 293 
of a mosquito. This mosquito appears thus to stand in the same relation to 
the owl Athene noctua as Glossina palpalis does to man. It is perfectly 
natural therefore to suppose that whatever cycle we may have found in the 
blood during infections with 7. gambiense, the real sexual phase may occur 
within Glossina palpalis or some other fly. From the informaticn which at 
present exists this line of criticism cannot be answered through observations 
upon infections with 7. gambiense. On this account, and pending further 
investigation in relation to 7’. noctuw, we have turned our attention to the 
parasites of the horse disease known as “ Dourine,’ and caused by 
T. equiperdum. Dourine* is not necessarily transmitted through any fly or 
intermediate host, but by direct contact between animals that have become 
infected. In this case we have, then, a trypanosome the life-history of which 
is not necessarily complicated by transference through an intermediate host. 
Whatever sexual phase there may be in the life-history of this parasite must 
be passed through in the body of the horse. 
If 7. equiperdum be injected into rats, the parasites multiply and kill the 
animal in about four days after their first appearance in the blood, which 
occurs about three days after the inoculation.t The disease in rats thus 
reaches a first maximum, and the animal dies without being able to overcome 
the invasion even temporarily, as would appear to be the case in infections 
produced by 7. gambiense in rats. The method of investigation has been as 
follows:—From the time the trypanosomes appear in the blood a very large 
number of slides have been prepared at short intervals up to death, and for a 
short time afterwards. Owing to the manner in which the disease is trans- 
mitted, special attention was paid to the fluids which collect in the various 
superficial swellings that are produced, for it naturally seemed possible that a 
phase of the life-history might occur in such positions in relation to the 
transmission of the parasites. The results of a prolonged investigation of this 
matter have, however, revealed nothing but the presence of ordinary trypano- 
somes,} and it is thus indicated that the transference takes place by means of 
the ordinary trypanosome encountered in the blood, possibly through the 
existence of slight abrasions on the animals that become infected, or more 
probably through the capacity of the trypanosomes to invade a mucous 
membrane, even if it is intact. 
* The strain we have used was obtained through the courtesy of Geheimrath Professor 
Ulenhuth, in Berlin. 
+ The best general account of dourine is contained in the works of Laveran and 
Mesnil’s ‘Trypanosomes et Trypanosomiases,’ Paris, 1904. 
t In rabbits, when few trypanosomes appeared in the blood it is interesting to note 
that in the fluids from the swollen vagina there existed many more parasites than in the 
blood. 
