220 Master Minds of Modern Science 



stomachs of thousands of mosquitoes without finding any 

 trace of the germ. 



Tired as he was, he began to work again, but a kindly- 

 fate must have watched over Ross that day. What fol- 

 lowed may best be told in his own words : 



I had scarcely commenced the search again when I saw a 

 clear and almost perfectly circular outline before me of about 

 twelve microns in diameter. The outline was much too sharp, 

 the cell too small, to be an ordinary stomach-cell of a mosquito. 

 I looked a little further. Here was another and another exactly 

 similar cell. I now focused the lens carefully on one of these, 

 and found that it contained granules of some black substances, 

 exactly like the pigment of the parasites of malaria. I counted 

 altogether twelve of these cells in the insect, but was so tired 

 out with the work and had so often been disappointed before 

 that I did not at the moment recognize the value of the obser- 

 vation. After mounting the preparation, I went home and 

 slept for nearly an hour. On waking, my first thought was that 

 the problem was solved, and so it was. 



Ross had discovered that the germs of malaria were 

 sucked by certain mosquitoes from the body of an infected 

 human being, and developed in the stomach-tissue of the 

 insect. He had made one of the greatest medical dis- 

 coveries, saved millions of lives, and yet he did not 

 appreciate what it all meant until he had slept ! That 

 incident reveals how utterly weary he was, in mind and 

 body, at the end of months of failure. 



The next day Ross dissected the last survivor of the 

 same batch of mosquitoes. Within its stomach he found 

 similar cells — only larger! That was conclusive. The 

 cells were parasites, and they not only lived, but grew 

 within the mosquito. The discovery was really two 

 discoveries, and each was of vital importance. As Ross 

 wrote afterward: 



We had to discover two unknown quantities simultaneously 

 — the kind of mosquito which carries the parasite, and the form 



