314 POPULAR SCIENCE MONTHLY. 



right track. One day Ross, whose station had in the meantime been 

 changed, caught some mosquitoes which had been feeding on a patient 

 the subject of tertian malaria. He kept the mosquitoes and after a 

 few days dissected them. He took the stomach out and placed it on a 

 slip with a little salt solution, covered it with a cover-glass and examined 

 it with a microscope. He was gratified to find lying amongst the trans- 

 verse and longitudinal muscular fibres a number of spherical bodies, 

 very sharply defined, and including a great many grains of intensely 

 black pigment exactly like those of the malaria parasite. Eoss was at 

 once struck with the similarity. After years of labor he believed he 

 had at last seen the malaria parasite in the tissues of the mosquito, 

 where we reasoned it ought to be; and he was right. At a subsequent 

 experiment on the malarial patient he found exactly the same bodies, 

 and on dissecting several mosquitoes at different intervals of time he 

 found that the parasite, which originally was six micro-millimetres in 

 diameter only, grew to sixty or eighty micro-millimetres, each parasite, 

 notwithstanding its growth and the lapse of time, still containing the 

 peculiar and most characteristic black pigment. Ross was now quite 

 sure that he had found the extra-corporeal phase of the malarial para- 

 site. Some of these preparations he sent home. I examined them 

 and showed them to a number of friends in London familiar with the 

 malarial parasite; they agreed with me, as Laveran also did, in believ- 

 ing that probably this indeed was the long-sought-for extra-corporeal 

 phase of the malarial parasite. Ross at that time had great difficulty 

 in getting opportunities for experiment on the human subject and in 

 procuring proper mosquitoes. He found that the mosquitoes in which 

 he had discovered these pigmented bodies were of a different species to 

 those on which he had formerly experimented, and that in this cir- 

 cumstance lay the explanation of his lack of success earlier as well as 

 the secret of his ultimate success. Failing to get sufficient opportunity 

 for experimenting on human malaria he turned to bird malaria. He 

 found that the sparrow of Calcutta, in a large proportion of instances, 

 contained in its blood a malaria-like parasite. Ross procured a number 

 of infected sparrows and let loose upon them a number of mosquitoes 

 of a species belonging to the genus culex. These mosquitoes, after 

 from one to ten days, he dissected and examined their stomachs. He 

 found in the stomach-wall pigmented bodies exactly similar to those 

 which he found in the stomach-walls of mosquitoes fed on human 

 malarial blood. He found that they increased in size and in a week 

 or ten days grew from six to eighty micro-millimetres in diameter. 

 When they became of considerable size they protruded like warts from 

 the surface of the insect's stomach and were included in a very definite 

 capsule. At this stage the capsule was filled with a vast number of very 

 minute rod-like bodies. These capsules, which now projected into the 



