﻿EXPERIMENTS IN MALARIAL TRANSMISSION. 529 



MOSQUITOES AND MALARIAL PARASITES. 



The examination of some five hundred blood smears from about fifty 

 patients in the "naval sick quarters" at Olongapo demonstrated the 

 presence of both tertian and sestivo-autumnal parasites, the former com- 

 prising about 65 per cent of the cases, the latter 35 per cent. In 

 no instance was the parasite of the quartan infection positively identified, 

 either microscojDically or clinically. Abundant material was therefore 

 continuously at hand for purposes of experimentation, and there was not 

 a single case in which any of the men objected to allowing themselves 

 to be bitten as many times as I desired. Many of the men were examined 

 only once, but a number had fifty to sixty slides made from their blood 

 in various stages of the development of the parasite and several of them 

 were bitten by not fewer than twenty-five to thirty mosquitoes, this, of 

 course, including some who were bitten as often as twelve to fourteen 

 times by the same insect. 



METHODS OF BREEDING. 



Two methods were used for obtaining the adult mosquitoes for purposes 

 of biting, one being to construct a cage over the breeding pond and to 

 take the adult females during the early morning ; the other to collect 

 many of the mature pupae at about 4 o'clock in the afternoon and to wait 

 for the emergence of the insects on the same evening, which in the great 

 majority of cases took place between 6 and 8 o'clock, although in fewer 

 instances the time was retarded until the next morning. It was found 

 that those emerging at eventide were ready and willing to bite by 9 or 

 9.30 o'clock at night, but that those which appeared in the early morning 

 seldom were ready to attack until the succeeding night after 6 o'clock. 



As soon as the adult mosquitoes emerged and had dried sufficiently 

 to be able to take flight, they were removed from the breeding receptacle 

 directly into glass tubes 16 centimeters long and 4 centimeters in diameter, 

 over one end of which were fastened, by means of rubber bands, pieces of 

 plain gauze. Wads of absorbent cotton were pressed into the other ends 

 of the tubes, but not too tightly to prevent a circulation of air. When 

 in the tube, the mosquitoes generally rested upon the gauze and this was 

 sprinkled daily with water, which the insects drank each time it was 

 applied. I attempted to observe whether the insects would copulate in 

 the tubes, but have never seen them do so, although eggs developed in one 

 or two females, so that fecundation had probably taken place. In placing 

 males and females into the tubes, care was taken to select only those 

 females which had not copulated in the breeding jar. They were care- 

 fully watched during emergence and removed, in some cases, even before 

 the integument had dried. None of these mosquitoes were used for 

 breeding purposes. 



