404 



MICROBIOLOGY 



The duration of the disease is from 1 to 4 months. Ex- 

 perimentally in the horse Lignieres found the shortest duration 

 of the disease to be 34 and the longest 134 days. The trypano- 

 somes appear in the blood in from five to eight days. 



TRYPANOSOMES IN THE BLOOD OF HEALTHY CATTLE. 



Crawley 1 describes a trypanosome which he found in the 



blood of seven American cattle, 

 and which he names Tr. Ameri- 

 canum, a new species. Crawley 's 

 work was done to repeat Miya- 

 jima's 2 cultural observation in 

 which he found that the trypano- 

 somes were derived from the 

 piroplasma. Crawley used the 

 blood of American cattle in 

 which no trypanosomes could be 

 found on microscopic examina- 

 tion. By following the method 

 of cultivation he procured try- 

 panosomes from each of the 

 seven cases. He was able to 

 show, however, that the trypano- 

 somes which he cultivated had 

 no connection with the piro- 

 plasma. Crawley found the 

 largest specimen to measure 

 about 38 /x in length, which did 

 not include all of the flagella. He estimates that the total 

 length is not unlikely 75 /A. It has a very short undulating 

 membrane. The kinetonucleus may be in front of, along 

 side of or behind the trophonucleus, but the two are always 

 close together. The short undulating membrane is explained 



Fig. 91. Trypanosoma 

 Americanum. Nos. 1 and 2, 

 from a 6 day bouillon culture; 

 3, 4 and 5 from a 10 day bouil- 

 lon culture. (After Crawley). 



1 Crawley. Bulletin 119, B. A. I., U. S. Dept. Agric., 1909. Also 

 reprinted in Jour, of Comp. Path, and Therap., Vol. XXIII (1910) 

 p. 17. 



2 Miyajima. Philippine Jour, of Science, Manila, 1907. 



