448 



SPECIFIC MICRO-ORGANISMS 



Plasmodiiun Kochi.— This is a malarial parasite which causes 

 a mild fever in monkeys. It is not transmissible to man. Other 

 species of malarial parasites have been recognized in these animals. 



Babesia^ Bigemina.— Smith and Kilborne • discovered this 

 organism in the red blood-corpuscles of cattle suffering from 

 Texas fever. The parasite is pear-shaped, 2 to 4m long and 1.5 to 

 2Ai wide and usually occurs in pairs within the erythrocytes. The 

 cytoplasm is quite clear without granules or pigment and contains 

 one or two chromatin bodies. Minute ameboid forms are^lso 

 found. Multiplication apparently takes place by longitudinal 





/ 



v^sAs). 



Pig. 213. — Babesia bigemina. Characteristic forms in the peripheral blood of cattle. 



X2000. {After Doflein.) 



division of the pear-shaped forms as well as by multiple division 

 of the ameboid forms. Macrogametocytes and microgametdcytes 

 have been recognized. The transmission of the parasite from 

 animal to animal is effected by the cattle tick, Boophilus bovis, 

 (Rhipicephalus annulatus) as was conclusively demonstrated by 

 Smith and Kilborne, the first instance in which such a relation 

 was proved for any blood-sucking invertebrate. The details of 

 the life cycle in the tick are unknown. It is certain however 

 that the infection is conveyed to the next generation of ticks 



' The generic name Pyrosoma bestowed by Smith and Kilborne in 1893 is incor- 

 rect, because this is the name of a genus of marine animals belonging to the Tuni- 

 cata. Babesia proposed by Starcovici in 1893 has the next claim to priority. 



