84 Messrs. J. G. Thomson and D. Thomson. 



shows a parasite with 15 daughter-cells, and we have found on several 

 occasions 16 spores, which we think is the usual maximum of daughter-cells 

 found in P. vivax, although again we find all stages, from 2 spores up to 

 16, according to the stage of development at which we examine the 

 cultures. We are quite certain that the spores are never so numerous as 

 in the malignant tertian parasite. In these cultures clumping has not been 

 found, and this explains why the parasites do not tend to be arrested in the 

 internal organs during sporulation, although when full grown they are much 

 larger than the malignant tertian parasite. 



The absence of clumping in the case of the benign tertian parasite 

 explains satisfactorily the absence of pernicious symptoms in this infection, 

 and hence the absence of comatose malaria, and it also explains why all 

 stages of this parasite are found in the peripheral blood, even up to 

 sporulation. 



The Morphology of the Benign Tertian Parasite in the Human Host. 



This, again, is identical with that which we have just described under 

 morphology in the culture tubes, figs. 21-30. The chief features in which 

 this parasite differs from P. falciparum are the large size of the containing 

 corpuscle, with the presence of Schufmer's dots, the straggling form of the 

 medium-sized parasites, the scattered pigment in the presegmenting stages, 

 and the smaller number of spores. These spores are larger than the spores 

 of the malignant tertian parasite. The pigment in the sporulating forms is 

 collected into a loose mass. With regard to the number of spores produced 

 by this parasite we have found as many as 24, but the most usual number is 

 16-18. In culture the largest number we obtained on three occasions 

 was 18. The following are the numbers of spores produced by P. vivax in 

 the human host, according to several observers : Eoss (1910) quotes the 

 figures of Grassi and Eeletti, 15-20 spores ; Marchiafava, Bignami, and 

 Mannaberg (1894), 16 spores ; Golgi quotes 14-19 spores ; Stephens and 

 Christophers (1908), 15 or more spores; Deaderick (1910) gives 12-26 spores 

 of tenest 1 6 spores. 



In our opinion Deaderick's figures are most correct. All stages of this 

 parasite are found in the peripheral blood, and the phenomenon of clumping 

 has never been observed. Eoss has taught recently that there are four splits 

 with this parasite, that is 16 spores; three splits with the quartan parasites, 

 that is 8 spores ; and five splits, or 32 spores, with the malignant parasite. 



