MASTIGOPHORA 41I 



of the infection, 8.8 per cent, is doubtless far below the actual 

 percentage, as many of the birds were not tested by the cultural 

 method. There are doubtless several species of bird trypanosomes 

 but. the most common form is Tr. avium. The length varies 

 from 25 to 70M and the width from 4 to 7^. 



Cultures are easily obtained by transferring the infected blood 

 to tubes of blood-agar and incubating at 25° to 30° C. The pro- 

 tozoa grow abundantly and, by weekly transfers, may be kept 

 under cultivation without special difficulty for an indefinite period. 

 Injection of cultures into birds is only rarely followed by appear- 

 ance of trypanosomes in the blood. 



The parasites persist in the blood of the birds for many months 

 and probably for years. They seem to be comparatively harmless. 

 The mode of transmission from bird to bird is unknown. 



Trypanosoma avium is a form of considerable importance in 

 the study of systematic protozoology because of the confusion of 

 trypanosomes and hemocytozoa by Schaudinn^ in 1904, who 

 regarded Tr. avium as merely an extracellular form of Hamopro- 

 teus nodua {danilewskyi?) (see page 433). This misconception, 

 together with the analogous assumption of similar relationship 

 between spirochetes of birds and the leukocytozoon of Ziemann, 

 Hamoproteus ziemanni, made by Schaudinn at the same time, 

 has exercised a profound influence upon the course of investiga- 

 tion in the groups of spirochetes, trypanosomes and hemocytozoa. 



Schizotrypanmn CruzL^Chagas discovered this organism 

 in 1907. It occurs in the blood in the Brazilian human trypano- 

 somiasis called cbreotrypanosis. Multiplication takes place 

 within endothelial cells, lymphocytes and other cells in the paren- 

 chymatous organs, and especially in the interior of muscle cells in 

 the heart and skeletal muscles.^ The dividing parasites are with- 

 out flagella and resemble the intracellular forms of Leishmania. 

 From these cysts the parasites escape into the blood, where they 



' Arb. a. d. Kais. Gesundheitsamte, 1904, Vol. XX, pp. 387-439. 

 ''Vianna: Memorias do Instituio Oswaldo Cruz, 1911, Vol. Ill, pp. 276-293. 

 Abstract in Sleeping Sickness Bull., 191 2, Vol. IV, pp. 288-293. 



