BINUCLEATA 43 



around Memel ; and a variety of Babesia, which causes the so-called 

 '.' bloody urine " in cattle turned out to grass. These varieties are 

 sporadic in their occurrence, and little reliance can be placed upon 

 them for practical purposes. Animals bred in laboratories and stables 

 are free from blood parasites, hence fresh material is only to be 

 obtained from free-living animals or by importation. There are, 

 however, many native wild animals, especially birds, as well as certain 

 foreign animals (lizards and tortoises), which are to be bought quite 

 cheaply from live-stock dealers, which harbour blood parasites in great 

 variety. The examination of these is much to be recommended, not 

 only as an introduction to the study of blood parasites in general, but 

 as a means of increasing our knowledge in this important, but little 

 understood, branch of parasitology. 



Birds offer excellent material for examination, especially singing 

 birds (Fringillidae) and birds of prey (owls and falcons). Infection 

 among them is comparatively frequent, and they are easily held and 

 handled in the laboratory. The life-history of a Plasmodium (a 

 member, that is, of the group to which the malaria parasite belongs) 

 can only be followed in this country by watching the development 

 of the Proteosoma of birds. The species Hcemoproteus and Leucocy- 

 tozoon, though theoretically important) are confined exclusively to 

 birds. But the very prevalence of blood parasites among birds 

 increases the difficulty of investigation, cases of mixed infection being 

 exceedingly common. 



Free-moving Flagellates (Trypanosomes) are not found with -any 

 frequency in the blood of birds. But Hcemoproteus, Leucocytozoon, 

 and, though in a less degree, Proteosoma, are by no means rare. 

 Hcemoproteus and Proteosoma occur in the Fringillidae (chaffinch, 

 sparrow, goldfinch, yellow-hammer, and others), while the birds of 

 prey (falcons, harfang and other owls) harbour Hcemoproteus and 

 Leucocytozoon. Acute infection is seen in young birds. Of exotic 

 bird species, that most readily obtainable is the rice-bird (Padda 

 oryzivora], which I have almost invariably found to contain Hcemo- 

 proteus, and my experiments are confirmed by those of Laveran. 



Other animals from which material may be obtained are the 

 following : 



(1) Among mammals, the rat and the hamster harbour Trypano- 

 somes. Eats bred in the laboratory do not contain parasites, but 

 infection is by no means rare in freshly caught grey rats. The 

 parasites once obtained, they may be permanently propagated by the 

 repeated inoculation of white rats (see p. 45). A similar parasite is 

 found in the hamster ; it was present in every animal examined by 

 L. Pfeiffer in the neighbourhood of Weimar, but was found by Wasie- 

 lewski in only two out of twenty-eight examples caught in the 



