MEDICINE, RECENT ADVANCES IN. 



345 



ANOPHELES. 



Eggs, greatly enlarged. 



had long been ruled out, as simply a biological 

 excuse for ignorance, it was evident that it must 



originate some- 

 where. It could 

 not be found in 

 the secretions of 

 the breath, or on 

 the skin of the 

 malaria patient, 

 and the only way 

 in which it was 

 possible to trans- 

 fer it from per- 

 son to person was by the direct transference of 

 the infected blood; and this, obviously, was ex- 

 tremely rare as a natural occurrence. 



But there was the evidence all about them; 

 hundreds of people in the tropics w r ere coming 

 down with the disease every day. They hunted, 

 and speculated, and experimented, and got no fur- 

 ther, until in 1894 Manson, whose curiosity had 

 been aroused by the apparent impasse, and who 

 was studying the germ, noticed that the flagel- 

 lated bodies, the curious devil-fish form observed 

 by Laveran, were never found in newly drawn 



ANOPHELES. 



Newly hatched and half-grown larva. 



blood, only making their appearance some mo- 

 ments after it was shed that is, if the blood was 

 killed immediately after it was drawn, and then 

 examined microscopically, none of these bodies 

 ever appeared, whereas if newly shed malarial 

 blood were allowed to stand a quarter of an hour 

 they could always be found. Here was something 

 of obvious importance, it being plain that what- 

 ever function these bodies had, it lay outside of 

 the human body. It soon occurred to Manson 

 that their function might be that of spores for 

 spreading the parasite in the external world, 

 and it seemed to him that -some suctorial in- 

 sect was very probably the agent for their dif- 

 fusion. There had been all sorts of theories regard- 

 ing the causation of such a wide-spread disease as 

 malaria, and among the theorizerswere believers in 

 the mosquito as one of the agencies. Dr. Koch 

 found certain tribes in German East Africa who 

 thought the disease entirely due to mosquito bites. 

 And nearly twenty years ago Dr. A. F. A. King an- 

 nounced his belief in the mosquito theory, as did 

 also Dr. Laveran himself in 1884. Indeed, Dr. 

 King, in a paper read before the Philosophical 



ri L e -YTT 1 . 1 1 OOO ,..',. 4-^ ** ** .,,-i ;..].. 



ing the theory. There lias also lately turned up 

 a letter giving a similar view, published in 1SH4 

 in the Muktataf, an Arabic review of (,'niro, 

 Egypt. But none of them had been in a position 

 to have the theory thoroughly tested, as was Dr. 

 Manson. 



Dr. Manson had observed, some year-, bei'oie, 

 that another parasite of human blood, a micro- 

 scopic worm called filar ia, was drawn with ihc 

 blood into the stomach of a kind of mosquito, und 

 found in that insect a congenial host, in which it 

 soon passed into another stage of its development, 

 and became an entirely different microbe, so far 

 as appearance was concerned. These metamor- 

 phoses are quite common among the lower forms, 

 of life, some of 

 them passing 

 through three, 

 four, and even 

 five separate 

 stages, in each 

 of which, un- 

 less they are 

 actually seen 

 to make the 

 change, they 

 wo\ild seem to 

 the observer to 

 be entirely dif- 

 ferent crea- 

 tures. Dr. Man- 

 son soon be- 

 came convinced 

 that a similar 

 series of events occurred in the development of 

 the malaria germ, and he fastened on the mos- 

 quito as the intermediate host. This was as yet 

 simply theory, however. 



Major Ronald Ross, of the Indian medical serv- 

 ice, during a visit to England, became deeply im- 

 pressed with Manson's arguments, and determined 

 to test the theory on returning to India. He was 

 at this time stationed at Secunderabad, and here, 

 he began work in April, 1895. He collected mos- 



ANOPHELES. 



quito larvae (the mosquito undergoes 



a series 

 de- 



Society of Washington in 1882, refers to an article of transformations, similar to those above de- 

 by a Dr. Josiah Nott, published in 1848, uphold- scribed, which are shown here) and bred 



