BABESIA. 305 



years before Ross's discovery of the transmission oi Plasmodium 

 prsecox by Culex mosquitoes. Not much, however, is known 

 of the actual development in the tick. Koch (1906 a) observed 

 that in the stomach of the tick the pear-shaped forms escaped 

 from the blood-corpuscles, became amoeboid, threw out long 

 spiky pseudopodia, associated in pairs, and gave rise to elongate 

 bodies with two nuclei and spiky pseudopodia at both 

 extremities. Fusion of the nuclei then took place, along 

 with the withdrawal of the pseudopodia. Christophers 

 (1907), who studied the development of B. canis in the tick, 

 doubted if the amoeboid stages were essential in the develop- 

 ment, and described motile club-shaped forms, which he 

 referred to as " zygotes " or " ookinetes." These give rise 

 to a globular stage, which divides by multiple fission into 

 sporoblasts and sporozoites. The sporozoites collect in vast 

 numbers in the salivary glands of the tick, and thence pass into 

 the Vertebrate when the tick feeds. Observations on the 

 development in cultures were pubhshed by Kleine (1906) and 

 by Nuttall and Graham-Smith (1908), and certain stages in 

 the tick were also described by Dschunkovski and Luhs (1909). 



The development of the parasite in the Vertebrate host 

 consists of multiplication by binary or quadruple fission 

 within the corpuscle. After destroying the corpuscles in 

 which they are lodged, the parasites become free in the blood 

 and penetrate other red corpuscles. The stages in the blood 

 were studied in great detail by Nuttall and Graham- Smith 

 (1906, 1907, 1908) and by Christophers (1907) in B. canis, 

 and a summary of their observations will be found under that 

 species. 



The organism remains in the blood of animals, that have 

 recovered from acute symptoms, for many years after its 

 apparent disappearance, as tested by microscopic examina- 

 tions, and inoculation of blood can produce infection in 

 a healthy animal. 



Cooper (1926 a) is of the opinion that infection with this 

 parasite is so widespread in India that probably in most 

 localities cattle become infected as young calves, at which 

 age they possess a high degree of resistance and recover 

 readily, and are subsequently immune, but continue to act 

 as carriers. Acute disease is liable to occur when adult 

 cattle are imported from countries where the species does not 

 exist, or when the immunity is broken down through the 

 effect of intercurrent disease conditions. 



Dennis (1930) described the structure of the nucleus of 

 B. bigemina and even noted the presence of a blepharoplast. 



Ray (1938) found the nuclear chromatin to be confined to 

 the apical portion of the parasite, with a circular row of fine 



SPOR. X 



