44 PRACTICAL PARASITOLOGY 



neighbourhood of Halle. This species of Trypanosome can only be 

 cultivated in the hamster. The blood parasites of the bat are very 

 interesting, but their study is rendered difficult by the fact that bats 

 do not live long in captivity. 



(2) Among reptiles, the most important are the lizard, Lacerta 

 muralis, and the tortoises, all of which harbour Haemogregarines. 

 The wall-lizard is frequently the host of Caryolysus lacertarum, while 

 varieties of Haemogregarines are always present in the tortoise. 



(3) Of amphibians, frogs are the most interesting, Trypanosomes 

 and Hsernogregarines (LanJcesterella) being frequently found in them. 



(4) Among fish, the Cyprinides are the most important. I have 

 rarely examined Crucians or tench without finding Trypanosomes. 

 When mammalian Trypanosomes are not available, these fish, though 

 they are as a rule only slightly infected, provide useful material for 

 demonstration purposes. 



(2) INOCULATION. 



In studying the blood parasites, it is essential to examine and 

 re-examine fresh material at different times, for in this way only 

 can the developmental stages of the different species be followed. 

 A sufficiency of material is necessary to investigation ; to obtain 

 this, the parasites (already discovered or obtained from other labora- 

 tories) should be propagated by the inoculation of living animals. 

 The resulting infection is generally acute in character, and the 

 animals may succumb after a definite and, generally, very short 

 time. This is the case with mice infected with the Trypanosomes 

 of tsetse-fly disease, and with dogs acutely infected with Babesia. 

 On the other hand, the animal experimented upon may overcome 

 the acute stage of the disease, but continue to harbour parasites in 

 very small numbers. This is the case with singing birds infected 

 with Proteosoma. In cases of mixed infection, it is occasionally 

 possible to isolate one variety of parasite by inoculation. Among 

 the parasites of birds, for instance, it is extremely easy to convey 

 Proteosoma by inoculation, while Hcemoproteus is not so readily 

 conveyed in this manner. Hence, by inoculation from a case of 

 mixed infection, the former parasite may be obtained. The inocula- 

 tion method has, however, proved its greatest value in the preser- 

 vation, for purposes of demonstration and research, of numerous 

 blood parasites which are pathogenic in hot countries. Thus, 

 Trypanosoma brucei, the originator of tsetse-fly disease, is now 

 cultivated in the laboratories of all countries owning African 

 colonies. 



It is a point of some importance that certain parasites are con- 



