302 Major Bonald Boss [March 2, 



determined by a comparison of the prevalence of different kinds of 

 gnat at different spots with the prevalence of fever at those spots. In 

 short, I was forced to rely simply on the careful examination of 

 hundreds of gnats, first of one species and then of another, all fed on 

 patients suffering from malarial fever — in the bone of one day finding 

 the clue I was in search of. Needless to say, nothing but the most 

 convincing theory, such as Manson's theory was, would have sup- 

 ported or justified so difficult an enterprise. 



As a matter of fact, for nearly two and a half years, my results 

 were almost entirely negative. I could not obtain the correct 

 scientific names of the various species of gnats employed by me in 

 these researches, and consequently used names of my own. Gnats of 

 the genus Culex (which abound almost everywhere in India) I called 

 " grey " and " brindled " mosquitoes ; and it was these insects which 

 I studied during the period I refer to. At last, the persistently 

 nugatory results which had been obtained with gnats of this genus 

 determined me to try other methods. I went to a very malarious 

 locality, called the Sigur Ghat, near Ootacamund, and examined the 

 mosquitoes there in the hope of finding within them parasites like 

 those of malaria in man. The results were practically worthless 

 (except that I observed a new kind of mosquito with spotted wings) ; 

 and I saw that I must return to the exact method laid down by 

 Manson. The experiments with the two commonest kinds of Culex 

 were once more repeated — only to prove once more negative. The 

 insects, fed mostly on cases containing the crescentic gametocytes of 

 Hsemomenas prsecox, were examined cell by cell — not even their 

 excrement being neglected. Although they were known to have 

 swallowed living Hsemarncebidae, no living parasites like these could 

 be detected in their tissues — the ingested Haeniamcebidas had in fact 

 perished in the stomach cavity of the insects. I began to ask 

 whether after all there was not some flaw in Manson's induction ; 

 but no — I still felt his conclusion to be an inevitable one. And it 

 was at this very moment that good fortune gave me what I was in 

 search of. 



In a collecting bottle full of larvae brought by a native from an 

 unknown source, I found a number of newly-hatched mosquitoes like 

 those first observed by me in the Sigur Ghat — namely, mosquitoes 

 with spotted wings and boat-shaped eggs. Eight of these were fed on a 

 patient whose blood contained crescentic gametocytes. Unfortunately 

 I dissected six of them either prematurely or otherwise unsatisfac- 

 torily. The seventh was examined, on August 20, 1897, cell by cell ; 

 the tissues of the stomach (which was now empty owing to the meal 

 of malarial blood taken by the insect four days previously being 

 digested) were reserved to the last. On turning to this organ I was 

 struck by observing, scattered on its outer surface, certain oval or 

 round cells of about two to three times the diameter of a red blood- 

 corpuscle — cells which I had never before seen in any of the hundreds 

 of mosquitoes examined by me. My surprise was complete when I 



