402 MICROBIOLOGY 



quantity of blood, whereas Tr. Brucei will not develop under 

 such conditions. Tr. Brucei in actively growing cultures pos- 

 sess a virulence nearly the same as that of the original nagana 

 blood. 



Trypanosoma Lewisi 3 varies greatly in size, when grown 

 on blood media, in cultures. There are minute forms which, 

 not counting the flagellum, are but 1 to 2 /* in length. Others, 

 typical in form, are not much longer than the diameter of the 

 red blood corpuscles while most of the spindle shaped cells 

 range from 15 to 20 /x. Some trypanosomes can be found 

 which are from 50 to 60 /x in length. The small forms may 

 explain how Novy and McNeal succeeded in infecting rats with 

 infected blood that had passed through a Berkefeld filter. 



Trypanosoma Brucei when grown in blood media show 

 slight variations in size. As a rule, they measure from 15 to 

 17 fji in length. It is longer and proportionately narrower than 

 Tr. Lewisi and its flagellum is not so long or distinct. 



TRYPANOSOMA EQUINUM VOGES. 



Place in nature. Tr. equinum is the cause of the fatal 

 epizootic disease among horses in South America known as 

 Mai de caderas. This trypanosome was discoveerd by Elmas- 

 sian in 1901. This discovery was promptly confirmed by 

 Voges l and others. The disease is quite widespread in Brazil 

 and other South American countries. It is more prevalent in 

 the dry season. It is essentially a disease of horses although 

 the mule and donkey are susceptible. Mice, rats, dogs, rab- 

 bits and monkeys are affected when inoculated with the in- 

 fected blood. Swine, sheep, goats and cattle are resistant but 

 their blood will, according to Laveran and Mesnil, harbor the 

 trypanosome for some time. It is reported by Elmassian and 

 Migone 2 that the rodent, Hydrochaerus capy~bara, is the "res- 



3 This is the Trypanosome of rats. It has been alleged to be 

 closely related to Tr. Evansi. 



1 Voges. Berliner tierarztl. Woch., 1901. 



2 Elmassian and Migone. Ann. de 1'Inst. Pasteur, Vol. XVIII 

 (1904) p. 587. 



