THE PATHOGENIC HEMOSPORIDIA 275 



blood, the latter with B. parvum in blood bouillon. In each of these 

 experimental cultures the forms assumed were highly different from 

 those in the blood. Kleine noted long protoplasmic filaments similar 

 to those seen by Koch ('06) in developmental stages in the tick, while 

 Miyajima gives descriptions and photographs of crithidia-like flagel- 

 lates, "five times the diameter of an erythrocyte" in length, which he 

 found in cultures and subcultures of Babesia parvum. Schaudinn 

 ('04) apparently found similar flagellated forms in smears of fresh 

 blood from cattle infected with Texas fever. The significance of these 

 flagellates, which, according to Miyajima, reproduce by longitudinal 

 division, cannot be interpreted until further observations and con- 

 firmations are made. 



The parasites reproduce by division while in the erythrocytes, and 

 thus form the typical twin forms characteristic of babesia, or larger 

 groups of from four to eight cells. Kinoshita describes an irregular 

 division or budding process which he regards as equivalent to schizogony 

 and merozoite formation in plasmodium (Fig. 107, F). Christophers, 

 however, does not confirm these findings, but describes the nucleus as 

 dividing by a modified mitosis (Fig. 108, D), or in some cases the blepha- 

 roplasts divide and the chromatin flows about the daughter halves, 

 which then push out from the periphery of the cell as buds. The buds 

 thus formed are not pinched off, as Kinoshita describes, but the pro- 

 toplasm of the cell flows into them in equal parts and the cell divides 

 by fission. In some cases further division of the daughter cells begins 

 before complete separation. The relative infrequency of multiple 

 forms in erythrocytes 1 is an argument against Kinoshita's view that 

 this represents schizogony. 



B. Transmission by Ticks and the Life Cycle of Babesia.- 

 Since Smith and Kilborne's epoch-making discovery of the tick as the 

 sole agent in the transmission of babesia, observations have accumu- 

 lated in regard to intermediate hosts and developmental changes of 

 the parasites in them, but, notwithstanding the number of observations 

 made, the life history of no form is yet known. 



The mechanism of transmission by ticks is often very complicated ; 

 according to Smith and Kilborne and Curtice, the insect becomes sex- 

 ually mature at its last moult while hanging to the skin of the ox. In 

 this condition the females are fertilized, gorge themselves with infected 

 blood, and drop to the ground, where they lay an enormous number of 

 eggs (up to 2000). Each egg case is supplied with a small quantity 

 of ox blood, which serves as food for the larva. The latter, very much 

 undeveloped, crawls upon a blade of grass, and if it manages to attach 

 itself to the hair of another ox it will live; if not, it dies of starvation. 



1 Erythrocytes with four parasites number from 2 to 5 per cent, of all infected corpuscles; 

 with eight, less than 0.05 per cent., and with sixteen, from 0.004 to 0.01 per cent., according 

 to Graham-Smith and Christophers (1907). 



