BY DR. A. JEFFERIS TURNER, M.D. LOND., D.P.H. CAMB. 105 
Ross, was so much impressed with Manson’s theory that 
he determined to verify the transmission of the malaria 
parasite by the mosquito if possible. His first observations 
were encouraging. He found that the process of ex- 
flagelation occurred in blood taken into the stomach of a 
mosquito much more freely than under other conditions. 
But here his progress stopped. He was not able to trace 
any development of the separated flagella, nor could he 
find in the tissues of mosquitos which had bitten malarious 
patients, any parasites that could be identified with 
the malaria organism. The research was an arduous and 
difficult one. He could not know what the organism 
he was looking for would be like, that is to say what form 
the malaria organism would assume in the mosquito. 
Again he could not know what species of mosquito, if any, 
were concerned in the matter, and at that time very little 
was known of the genera and species of mosquitos. 
For two years, with admirable zeal and perseverance, 
Ross devoted his spare time to this quest, and dissected 
and microscoped many hundreds of mosquitos without 
success. Then having by chance obtained a few specimens 
of a mosquito hitherto unknown to him, and having fed 
them on malarious blood, he found on dissection, several 
days later, some round pigmented cells in the stomach 
of the mosquito. Such cells he knew were not normally 
present in the stomachs of mosquitos, and at last he had 
found his clue. Unfortunately, at this stage, official duties 
prevented his carrying the research further, and the next 
ray of light came from an American observer, MacCullum. 
MacCullum observing a parasite in the blood of birds, 
the halteridium, which is allied to that of human malaria, 
found that after exflagellation, the separate flagella swam 
about until they encountered and fused with certain rounded 
forms of the parasite, and that these thereupon assumed 
a vermicular form and exhibited active movements. That 
in fact the process was one of sexual conjugation, followed 
by a fresh stage of development. 
At this stage, the Indian Government took a very 
enlightened step. They relieved Ross of his military 
duties, and sent him to a well-equipped laboratory in Calcutta 
to investigate the mosquito-malaria theory. It happened 
