SPOROZOA 1101 



the mature cyst, these collect in large numbers in the salivary glands 

 and ducts. 



The life history of the parasite is seen to be like that of proteosoma 

 and malaria, except that the asexual or schizogenous cycle appears to 

 be lacking. 



Proteosoma (plasmodium) prseoox. This parasite is a typical 

 representative of the sporozoa, and is interesting historically, since 

 it was the one with which Ross worked in 1898, when he first 

 demonstrated the part played by the mosquito in "bird malaria." 



Grassi and Feletti described the parasite in 1890 under the name 

 of hemameba precox. It is widely distributed geographically, and is 

 common in the blood of small birds, sparrows, robins and larks. It 

 can be propagated in the laboratory in the blood of canaries with- 



FIG. 147. PROTEOSOMA PKECOX IN BLOOD OF FIELD LARK. A. Young parasite in 

 blood cell; 5, Half -grown parasite which has pushed aside nucleus of blood cell; 

 C, Parasite with clump of pigment and many nuclei; D, Division into many 

 merozoites. (After Doflein and Wasielewski. MacNeal, "Pathogenic Micro- 

 organisms," published by P. Blakiston's Son & Co.) 



out great difficulty; sparrows, however, do not long survive in cap- 

 tivity unless kept in round glass jars, where they cannot injure them- 

 selves by dashing against the walls. The blood for examination is 

 obtained from the cephalic wing vein, close to the body, which is 

 nicked with a razor, and the blood taken up in a capillary glass tube 

 containing a little citrate solution. To inoculate a new bird, it is 

 sufficient to inject a small quantity of citrated blood from an infected 

 canary into the breast muscles of the new bird, transferring to a new 

 host at intervals of a month or less. Because it is not difficult to 

 keep on hand, this organism may be used for class study in localities 

 where malarial cases are infrequent. There is no apparent reason 

 for placing it in a different genus from the malarial parasites. 



The entire asexual cycle, schizogony, may be studied in the periph- 

 eral circulation, as in quartan malarial fever. 



In nature it is transmitted by both culex and stegomyia (Aedes 



