Insects and Disease 623 



source I found a number of newly hatched mosquitoes like those first obser\-ed 

 by me in 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 unsatisfactorily. The seventh was examined, on August 20, cell 

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

 of malarial blood taken by the insect four da}'s previously being digested) 

 were reserved to the last. On turning to this organ I was struck by observ- 

 ing, scattered on its outer .surface, certain oval or round cells of about two 

 or three times the diameter of a red blood-corpuscle — cells which I had never 

 before seen in any of the hundreds of mosquitoes examincfi by me. My 

 surprise was complete when I next detected within each of these cells a jew 

 granules of the characteristic coal-black melanin oj malarial jever — a substance 

 quite unlike anything usually found in mosquitoes. Next day the last of the 

 remaining spotted-winged mosquitoes was dissected. It contained precisely 

 similar cells, each of which possessed the same melanin; only the ceUs in 

 the second mosquito were somewhat larger than those in the first. 



" These fortunate observations practically solve the malarial problem. 

 As a matter of fact, the cells were the zygotes oj the parasite oj remittent jever 

 growing in the tissues oj the gnat; and the gnat with spotted wings and boat- 

 shaped eggs in which I had found them belonged (as I subsequently ascer- 

 tained) to the genus Anopheles. Of course it was impossible absolutely 

 to prove at the time, on the strength of these two observations alone, that the 

 cells found by me in the gnats were indeed derived from Ha-'mamocbidas 

 sucked up by the insects in the blood of the patients on whom they had 

 been fed — this proof was obtained by subsequent investigations of mine; 

 but, guided by the presence of the typical and almost unique melanin in the 

 cells, and by numerous other circumstances, I myself had no doubt of the 

 fact. The clue was obtained; it was necessary only to follow it up — an 

 easy matter. . . . 



"Early in 1898, mainly through the influence of Dr. Manson, Sir H. W. 

 Bliss, and the United Planters' Association of Southern India, I vv-as placed by 

 the Government of India on special duty in Calcutta to continue my inves- 

 tigations. Unable to .work with human malaria — chiefly on account of the 

 plague-scare in Calcutta — I turned my attention to the Hsmamocbidas of 

 birds. Birds have at least two species of Hasmamcebidae. I subjected a 

 number of birds containing one or the other of these parasites to the bites 

 of various species of mosquitoes. The result was a repetition of that pre- 

 viously obtained with the human parasites. Pigmented cells precisely simi- 

 lar to those seen in the .4 nophcles were found to appear in gnats of the species 

 called Culex jatigans Wiedemann, when these had been fed on sparrows and 

 larks containing Hcemamoeba relicta. On the other hand, these cells were 



