Trypanosomes of the Domestic Animals in Nyasaland. 49 



that a short sojourn in the blood of the goat has almost nullified the virulence 

 of the parasite for the monkey. 



T. simice belongs to the same group as T. pecorum, and it is curious that 

 in the latter species this loss of virulence also occurs. If T. pecorum, which 

 is usually more or less infective to the monkey, dog, and rat, lives for some 

 time in the blood of the goat, it loses its power of infecting the other animals. 

 This has given rise to the erroneous idea that a separate species — T. nanum — 

 exists. T. nanum is in truth nothing but a strain of T. pecorum which has 

 lost its virulence for these other animals by its passage through the goat. 



T. simice is also like T. pecorum in general appearance, and in fact it is 

 often difficult or impossible to distinguish between a short individual of the 

 former species and a long one of the latter. The average length of T. simice 

 is 17'5 microns, with a minimum of 14 ; the average length of T. pecorum is 

 14 microns, with a maximum of 18. When the coloured plates of the two 

 species are compared this resemblance is at once seen. There is the same 

 well-developed undulating membrane, the same oval nucleus, situated about 

 the middle of the body, and the same eccentrically-placed micronucleus, often 

 appearing to project beyond the margin, as noted in the description of the 

 morphology of T. simice. 



These two species, however, differ essentially in their action on animals. 

 Whereas T. simice expends its virulence on monkeys and pigs, T. pecorum is 

 especially fatal to cattle, goats, sheep, and dogs. 



Animals Susceptible to Trypanosoma simle, sp. nov. 

 Table 1. 



Date. 



No. of 

 expt. 



Source of Tirus. 



Period of 

 incubation 

 in days. 



Duration 

 of disease, 

 in days.* 



Remarks. 



1912. 

 April 24... 



„ 24... 

 July 17... 



„ 17... 



Sept. 25... 



Not. 5... 



„ 5... 



1913. 

 Mar. 5... 



„ 5... 

 VOL. 



485 

 486 

 904 

 945 



1240 

 1238 

 1240a 



1980 

 1981 



* Dura 

 LXXXVII 



„ 405 



From Goat 653 



„ 653 



From Monkeys 1258 



and 1259 

 From Monkey 1541 ... 



1541 ... 



1910 ... 

 1910 ... 



tion includes the days of 

 — B. 



Cattle. 

 Antelope. 



incubation ; 







it dates froi 



NeTer showed trypanosomes. 



>> ?) 



>> >) 



Duiker. Never showed try- 

 panosomes. 



Reedbuck. Never showed try- 

 panosomes. 



Duiker. Never showed try- 

 panosomes. 



Reedbuck. Never showed try- 

 panosomes. 



Duiker. Never showed try- 

 panosomes. 

 n day of infection. 



E 



