PROTOZOA 405 



on the ground that the nuclear system is pushed forward 

 at the junction of the anterior and middle thirds. Crawley 

 concludes that Tr. Americanum lives in all probability as 

 a typical trypanosome in the blood of perhaps 75% of adult 

 and yearling cattle, but that it is not present in young calves. 

 He found that the removal of the trypanosomes from the 

 circulating blood stimulates their multiplicative energy, 

 presumably as the result of a cooler environment. He 

 found that this trypanosome could be cultivated in ordinary 

 bouillon made from either beef or mutton and that the average 

 time required for the trypanosomes to be readily detected in 

 the tubes was about 3% days. He found seasonal fluctuation, 

 trypanosomes being more abundant in the spring and summer 

 than they are in the autumn. Recently, Stockman 3 has found 

 trypanosomes in the blood from 6 of 10 animals in England 

 that were 'going to South Africa and were being immunized 

 against piroplasmosis. The evidence of Crawley and Stock- 

 man indicates the distribution of trypanosomes in cattle. 

 Frank and Frosch, 4 in 1909, found living specimens in the 

 spleen pulp of an ox which had died from what was thought 

 to be anthrax or blackleg. Pathogenic bacteria were not found. 

 Frosch 5 described this parasite and named it Tr. Franki. 

 Knuth, 6 who studied the same material, describes the trypano- 

 some as from 20 to 40 ju in length with a breadth of about 2 /* 

 and that it resembles Tr. Theileri more closely than any other 

 species. Frank and Frosch considered it to be pathogenic. 

 Mayer 7 considers it a trypanosome that had previously been 

 found exclusively in the tropical or sub-tropical countries. He 

 quotes from a number of authors who have found trypano- 

 somes occurring sporadically in cattle, mostly, however, in 

 Asia and Africa. 



3 Stockman. Jour. Comp. Path, and Therap., Vol. XXIII (1910) 

 p. 189. 



4 Frank and Frosch. Zeit. f. Infektionskrankheiten. . . der 

 Haustiere, Bd. V (1909) p. 330. 



5 Frosch. Ibid., p. 316. 



8 Knuth. Ibid., Bd. VI (1909) p. 39. 

 7 Mayer. Ibid., p. 46. 



