MAJOR ROSS'S RESEARCHES 143 



men showed the same characteristic cells with the 

 same characteristic pigment ; but the peculiar cells, 

 quite unlike anything hitherto met with in the mos- 

 quito's body, were larger and further developed. 

 * These fortunate results practically solved the malaria 

 problem.' 



Without following in detail the various stages of 

 the further investigations carried on by Major Ross, 

 we must endeavour to give an account of the final 

 results obtained by him and later investigators. 

 Being unable to obtain material for the study of 

 malaria in man owing to the scare caused by the out- 

 break of plague amongst the natives, Ross worked 

 out the life-history of an allied organism which causes 

 malaria in birds. It is to the brilliant researches of 

 the Italian school prominent among whom are Grassi, 

 Bastianelli, and Bignami that we owe the first com- 

 plete accounts of the life-history of the human parasite. 

 It has already been explained that some of the para- 

 sites do not form spores, but persist in a more or less 

 unchanged condition whilst in the blood of man as 

 gametocytes. We have also seen that when removed 

 from the human body some of these gametocytes 

 throw off actively mobile filiform bodies. In 1897 

 MacCallum of Baltimore showed what these filiform 

 bodies really are. Certain of the gametocytes do not 

 produce them, but lie passively still on the microscope- 

 slide, or in the blood within the mosquito's stomach. 

 These are destined to form the female cell ; the fila- 

 mentous bodies which break off from the first-named 

 gametocyte were seen by MacCallum to fuse with 

 them, and, in fact, to play the part of the male cell or 

 spermatozoon. This, in fact, happens when a mos- 

 quito feeds on a malarious patient. The gametocytes, 

 unchanged in the blood of man, as soon as they reach 

 the stomach of the insect, swell and burst from their 

 red corpuscle. The male gametocyte throws off the 



