﻿396 The Philippine Journal of Science 1914 



The number of gametes in the blood of patients was deter- 

 mined approximately by making a differential count of gametes 

 and leucocytes. In a few of the earlier experiments the gametes 

 were not counted. Following these, differential counts were 

 made on thin blood smears, from 200 to 500 leucocytes being 

 counted in each case. In the latter experiments, which include 

 all of the more exact quantitative experiments, the differential 

 counts were made on thick blood smears, in which from 1,500 

 to 3,000 leucocytes were counted. Darling (1910) has estimated 

 that the limits of infectiousness of man to mosquitoes is about 

 1 gamete to 500 leucocytes, or 12 gametes to a cubic millimeter 

 of blood. No patient was intentionally used in which the gametes 

 approached the limits of infectiousness as estimated by Darling, 

 and an effort was made to obtain patients for our experiments 

 with as high a gamete count as possible in order to increase 

 the probabilities of infection of the mosquitoes. Every time 

 the mosquitoes were fed on a patient, a blood smear was taken 

 for a gamete count in order to have information of the number 

 of gametes in the blood at the time of feeding. 



Some of the patients employed for the biting experiments 

 were on quinine treatment. Darling (1910) claims, howeyer, 

 that this does not affect the infectiousness of the blood for 

 mosquitoes. This question will be considered at length in the 

 discussion of our experiments. 



Thomson (1912) found that in a case of subtertian malaria, 

 treated with quinine until all of the schizonts were killed, the 

 gametes persisted for about twenty-one days; that is, the ga- 

 metes of Plasmodium prxcox {falciparum) are not affected by 

 quinine and their life is about three weeks. This has not 

 been wholly our experience. In tertian and quartan infections 

 the gametes quickly disappear from the blood under quinine 

 treatment, and frequently also without any treatment. On the 

 other hand, the gametes of subtertian malaria are much more 

 persistent. They have frequently persisted for weeks, whether 

 or not the patient was under quinine treatment. Usually, 

 however, the gametes after reaching the maximum gradually 

 diminish in number whether or not the patient is being treated. 

 Many of the gamete carriers showed few or no vegetative forms 

 of the parasites in their blood, and frequently presented no 

 symptoms over considerable periods of time. These were kept 

 off quinine and used repeatedly for biting experiments. 



