﻿398 The Philippine Journal of Science 1934 



mosquitoes that bit from those that did not bite the infected 

 patient nor the males from the females. The mosquitoes were, 

 when possible, given several opportunities to feed on blood on 

 successive evenings, and it was presumed that the majority- 

 availed themselves of the opportunity. However, it is probable 

 that a greater or less number of them failed on every occasion 

 to suck blood. In the later experiments, in order to obtain an 

 accurate comparison of the susceptibility of the different species 

 proved to be capable of carrying malaria, the different species 

 were fed simultaneously on the same gamete carrier and then 

 the females full of blood were separated from the empty or 

 doubtful females and the males. This was accomplished by 

 feeding the mosquitoes in large numbers in the cages in the 

 ordinary manner and then removing them individually from the 

 cages in test tubes and examining them with a hand lens to 

 determine whether or not they were full of blood. This was 

 determined by the distinct red color of the abdomen of those 

 which are gorged with fresh blood. The examination must be 

 made shortly after feeding on the patient, as the blood becomes 

 dark in color a few hours after it is ingested. The swollen 

 condition of the abdomen is not a safe criterion, especially in 

 the dark-bodied species like Anopheles barbirostris, because this 

 condition may be due to engorgement with water or raisins 

 used as food. Those full of blood were then liberated together 

 in a fresh cage. The mosquitoes in the comparative cages con- 

 taining the different species fed simultaneously on the same 

 patient were then dissected on the same date to determine the 

 proportion of infections and the relative number of oocysts in 

 the infected individuals. 



DISSECTION OF THE MOSQUITOES 



In the experiments to determine the capability of the different 

 species to become infected, the mosquitoes were kept alive from 

 five to ten days after the last feeding on infected blood before 

 dissection ; that is, long enough to obtain well-developed oocysts, 

 but not until the sporozoites had escaped from the oocysts. The 

 advantages of such early dissections for the purpose intended 

 are that there is less loss of the mosquitoes by death and a 

 considerable saving of time in the dissections, as it is only 

 necessary to examine the mid-gut. The dissection of the salivary 

 glands takes much more time and careful work. 



The mosquitoes to be dissected were killed in the cage by a 

 few drops of chloroform. The males when present were re- 



