THE PARASITE OF MALARIA IN THE MOSQCTITO 45 



the insect, but was so tired with work, and had been 

 so often disappointed before, that I did not at the 

 moment recognise the value of the observation. After 

 mounting the preparation I went home and slept for 

 nearly an hour. On waking, my first tliought was that 

 the problem was solved, and so it was." 



Then Ross proceeds to add : 



" The mind long engaged with a single problem 

 often acquires a kind of prophetic insight, apparently 

 stronger than reason, which tells tlie truth, though the 

 actual arguments may look feeble enough when put 

 upon paper. Such an insight is mainly based, 1 sup- 

 pose, on a concentration of small probabilities, each of 

 which may have little weight of itself ; but in this case, 

 at all events, the insight was there, and spoke the 

 truth." 



Up to this point Ross had proved that the parasite 



of malaria (Laveran's corpuscles), when sucked into the 



stomach of mosquitos in a meal of blood after the 



mosquito had bitten a person with malaria, underwent 



further development. 



" I had traced," he says, " the development of the 

 pigmented cells up to their maturity and subsequent 

 rupture and discharge of their contents into the body 

 cavity of the grey mosquitos. I could not see at the 

 moment what happened to these contents, yet upon 

 this point depended the vastly important question of 

 the root of infection in malaria. ..." 



" Hitherto my mosquitos had been dissected in 

 water or a weak solution of salt, and I had had no time 

 for methodical staining. A strong salt solution was 



