﻿IX, B, 5 Walker and Barber: Malaria in the Philippines 399 



moved, and each female, as she was removed from the cage for 

 dissection, was carefully examined for the identification of the 

 species, as it is not uncommon for two or more species to be 

 represented in the same cage. When only the mid-gut was dis- 

 sected, the thorax and head were preserved for later confirma- 

 tory identification. 



The dissection of the mid-gut was performed according to the 

 method described by Stephens and Christophers (1906). The 

 mosquito is laid on a glass microscope slide over a white card 

 on which is a blackened area. Over the white background, 

 the abdomen of the mosquito is cut off at its junction with the 

 thorax with a sharp needle. The abdomen is then moved over 

 the black background, and a drop of physiological salt solution 

 is placed upon it. The abdomen is held at the proximal end 

 by one dissecting needle, while a second needle is pressed on the 

 terminal segment and gentle traction exerted. With proper care 

 and experience, the intestinal tract and the ovaries will be drawn 

 out intact, attached to the terminal segment. If the hind-gut 

 breaks off, leaving the mid-gut in the abdomen, it can be dis- 

 sected out by slitting the wall of the abdomen with dissecting 

 needles. The mid-gut is then cut off, and all of the Malpighian 

 tubules are carefully removed with the needles, otherwise they 

 tend to lie over the mid-gut and obstruct the microscopic view. 

 All of this dissection should be made under a simple lens sup- 

 ported by a holder. A cover glass is then placed over the mid- 

 gut, and it is examined first with the low power and then with 

 the high-power dry lens of the compound microscope for oocysts. 

 At the period of development at which our dissections were 

 made, the oocysts could always be identified with a Zeiss DD 

 objective, and usually with the AA objective. The immature 

 oocysts of this age appear against the granular background of 

 the gut wall, as round or slightly oval, transparent, structureless, 

 feebly refractive bodies, 19 to 42 microns in diameter, and 

 having a definite wall. Their identity is made certain by the 

 presence of malarial pigment in the protoplasm. The older 

 oocysts, in which the sporoblasts or sporozoites have developed, 

 are larger, more granular, and darker in appearance, and the 

 sporoblasts or sporozoites in them are readily recognized with 

 the higher magnification. 



In order to determine whether the malarial parasites were 

 capable of attaining complete development in the several species 

 of the mosquitoes, it was considered necessary to give the para- 



