SPOROZOA 1135 



of ticks in four and a half or eight months, depending on the plan 

 followed. For economic reasons, lack of sufficient pasture land, etc., 

 this plan has not been widely adopted. A second plan, that of dipping, 

 has been more successful. The cattle are driven through a large dip- 

 ping vat at intervals of two weeks (never more than three must 

 elapse) until they and the pasture are free from ticks. The fluid in 

 the dipping vats is an alkaline solution of arsenic; oil dips are little 

 used at present. Arsenical dips are cheap, easily prepared and effi- 

 cacious, two or at most three dippings, at ten-day intervals, being suf- 

 ficient to free heavily infected cattle, and if they can then be put on 

 tick-free pastures the problem is solved. If no tick-free pastures are 

 available, dipping must be continued, as above, until the animals 

 remain permanently free. 



The prevention of tick-borne disease is to be solved, therefore, by 

 tick eradication, and experience in the Southern states has shown this 

 to be a practical measure. 



SUB-CLASS NEOSPORIDA 



SARCOSPORIDIA 



These organisms belong to the sub-class Neosporidia of the Sporo- 

 zoa, because the spore formation commences before the completion 

 of growth. They have been known since 1843, when Miescher dis- 

 covered ''tubes" in muscle fibers, visible to the naked eye as fine, 

 white, opaque filaments. They have been found in deer, cattle, sheep, 

 swine, rabbits and man, and occasionally in birds and reptiles. Al- 

 though long known, our knowledge of them is still defective. In sheep 

 they are the cause of severe epizootics, and in mice they are fatal: 

 otherwise they seem to be harmless parasites and in rare instances 

 have been accidentally found at autopsy in man. 



The method of transmission is not definitely known. Theobald 

 Smith was able to infect mice with Sarcocystis m-uris by feeding mus- 

 cles from infected mice, and Darling was able to infect guinea-pigs 

 in the same manner. In nature it is probable that infection occurs 

 through the intestinal tract. They are exceedingly common in some 

 localities and may be seen in most abattoirs; they luive been found in 

 ninety-eight per cent of swine, ninety-eight per cent of sheep, and 

 commonly in deer and mice. 



