Growth and Sporulation of Tertian Malarial Parasites. 83 



maximum sporulation. All of them contained over 20 spores, and 

 J 3 per cent, had 32 spores. "We think that there can be little doubt that we 

 have proved conclusively, both from observations in the culture tube and in 

 human host, that P. falciparum is capable of producing a maximum, under 

 favourable circumstances, of 32 spores. This is a much larger number 

 than has been previously given in the writings of competent observers. 

 Eoss (1912) quotes the figure of Welch (1897) at 6-20 or more spores. 

 Later, however, from observations made by himself and D. Thomson, he 

 taught that the maximum number was 2 to the power of 5 or 32, 

 Marchiafava, Bignami, and Mannaberg (1894) state that the numbers vary 

 from 8 to 15, while the following authors give the numbers as follows : 

 Stephens and Christophers (1908), 8-10 ; Deaderick (1910), 5-25 and even 30 ; 

 Gulland and C4oodall (1912), 8-15. It is probable that these discrepancies 

 are due to two reasons, (a) observations of autopsy smears in which the 

 sporulation had not reached its full maturity, and (b) observations on 

 autopsy smears of patients to whom quinine had been given before death. 

 In such cases incomplete and atypical sporulation is seen. We do not claim, 

 of course, that 32 spores are always produced even under favourable condi- 

 tions without quinine administration. It is likely that the numbers produced 

 vary considerably, just as in the case of benign tertian, which produces 

 numbers varying from 16 to 26. 



The Morphology of P. vivax in Gultv/re. 



Here we are studying a parasite in which all stages from small rings up to 

 full sporulation may be seen in the peripheral blood. Sporulation does not 

 necessarily occur in the internal organs, and it is quite usual to find these 

 forms in ordinary peripheral blood smears. When cultivating this parasite, 

 therefore, it is important to draw the blood from the patient when the young 

 forms predominate, so that it is then certain whether or not we are obtaining 

 further development in the culture tubes. In the culture illustrated in 

 Plate 10, figs. 21-30, we obtained the blood when young rings (fig. 21) 

 predominated and no segmenting forms were found. After eight hours' 

 incubation at a temperature of 39° C, a marked increase in size of the 

 parasites was noted (figs. 22, 23, and 24), and pigment was now evident, 

 being scattered throughout the protoplasm in fine granules. This arrange- 

 ment of the pigment in P. vivax is in marked contrast to what occurs in 

 P. falciparum, where the pigment always becomes arranged into a dense 

 circular mass from the commencement. After 20-29 hours' incubation 

 (figs. 25-30) sporulation was seen at different stages, the pigment being 

 collected into a loose mass of granules in the centre of the parasite. Fig. 29 



