MALARIA. 



655 



the organisms of avian malaria, and later in rela- 

 tion to the parasites of human malaria. 



In the same year Eoss found the pigmented, 

 half-moon shaped parasites of sestivo-autumnal 

 fever in the stomach of the anopheles mosquito. 

 Through the work of Koss and others it is now 

 established that the malarial parasite undergoes 

 further development, a sexual cycle, in anopheles, 

 and that man is inoculated only by the bites of 

 such infected insects. From the standpoint of 

 the zoologist, man is an intermediate host for the 

 parasite, since the latter undergoes its higher de- 

 velopment only after it reaches the mosquito. 



The malarial parasites of man belong to the species of 



i co -i /-N T ~^JL i -i Plasmocliui 



class or bporozoa ; order, (Joccidiomorpna ; family, 

 Hemosporidia ; genus, Plasmodium. The follow- 

 ing are the names given to the three species: 1. 

 Plasmodium prcecox (parasite of aestivo-autumnal 

 fever) ; 2. Plasmodium vivax (of tertian fever) ; 

 3. Plasmodium malarice (of quartan fever). 



When the blood of one suffering from tertian Tertian 

 fever is examined at the end of the febrile parox- 

 ysm, or at the beginning of the afebrile stage, the 

 parasites are found within the erythrocytes as pale, 

 rather clear bodies, about one-fifth the diameter of 

 the corpuscle, and in fresh specimens showing an 

 active ameboid movement. They are very difficult 

 to recognize in unstained specimens. They increase 

 in size gradually, and after eighteen hours, when 

 they begin to acquire pigment, they are recognized 

 more easily. After twenty-four hours the pig- 

 ment has increased markedly and the erythrocytes 

 are swollen and pale. In stained preparations the 

 periphery of the parasite stains more deeply than 

 the center and gives it a pronounced ring form. 



