BINUCLEATA 45 



fined to certain hosts, while others may be transmitted to animals 

 of widely different species. Thus, Babesia canis will live and develop 

 only in the dog, Trypanosoma lewisi only in the rat, and T. criceti only 

 in the hamster ; but the greater number of pathogenic Trypanosomes 

 are transmissible to all kinds of laboratory subjects. The study of 

 specific parasites is facilitated by choosing animals for experiment 

 which, under normal conditions, are never infected with the organism 

 under investigation. This applies to all the species already men- 

 tioned (indeed, that pathogenic to man can only be studied by 

 inoculating animals), and also to the Trypanosome of rats, which 

 may be transmitted to white rats. It applies, moreover, to Proteo- 

 soma, which may be transmitted to canaries, a point of considerable 

 practical importance to the student. 



The inoculation method is very valuable for observing the Trypano- 

 somes of mammals, the Proteosoma and the Babesia. 



(1) Inoculation with the Trypanosomes of rats should be performed 

 as follows : Blood is drawn from the artery of a chloroformed rat by 

 means of a Pravaz's syringe. It is diluted with sterile normal saline, 

 and a quantity of 3 to 5 c.cm. is then injected, either subcutaneously 

 or intraperitoneally, into the body of a white rat. The period neces- 

 sary for incubation, that is, until the appearance of Trypanosomes 

 in the blood, is generally about twenty-four hours, though it may 

 occasionally be as long as four days. The period of infection lasts 

 from three weeks to six months. There are, as a rule, no pathological 

 appearances. 



Eats may be used for the cultivation of the tsetse Trypanosome. 

 They die very quickly, however (in six to nine days), and this neces- 

 sitates frequent re-inoculation, if living Trypanosomes are to be kept 

 for any length of time. The incubation period is up to two days. 

 Mice are more convenient for this purpose, but they die in from three 

 to six days. 



(2) Proteosoma should be conveyed by the following method : 

 A small quantity of blood is withdrawn from the wing vein of the 

 infected bird, or, if the bird is freshly or quite recently killed, the 

 blood may be taken from an artery. It is diluted to six times its 

 bulk with sterile normal saline, and of this mixture 0'2 to 0*3 c.cm. is 

 injected into the breast-muscle of a canary. The parasites generally 

 appear at the end of about a week, and by the third week they are 

 very numerous. 



When it is desired to bring about a strong infection for demonstra- 

 tion purposes, and the subjects for examination are canaries which 

 have already been infected, but in which the acute stage is passed, 

 parasites having become so scarce in the blood that they are no 

 longer demonstrable, v. Wasielewski recommends that two birds 



