230 THE RISE AND FALL OF DISEASE 



lower animals finds its parallel in man. And in effect, 

 in 1904, two sets of investigators working indepen- 

 dently in Africa proved that the well-known spirillum 

 of relapsing fever, the parasite which sets up this 

 disease in man. was transmitted from man to man by 

 the bite of a tick, tlie OjiiitJiodoros //loi/Jjdfd, the disease 

 induced receiving in consequence the name of Tick 

 Fever. 



Two of the investigators who had been sent out 

 by the Liverpool School, Drs. Dutton and Todd, 

 proved the further interesting facts, namely, that the 

 parasite taken up by the parent tick in its meal of 

 blood could pass into the egg and larva ; in other 

 words, could pass into the body of tlie insect, — facts 

 which Pasteur had shown to occm- in the case of silk- 

 worm disease. The infected silkworm moth transmitted 

 to the egg, and these to the worms, which developed 

 from them, the virus of that disease. So with these ticks. 

 As the result of biting a man harbouring the parasite, 

 they infected themselves and their offspring, thus pro- 

 ducing a miniature epidemic amongst themselves and 

 their brood ; and presumably these infected or diseased 

 ticks are capable of communicating the parasite to 

 man when they attack him. It was whilst engaged 

 upon this research that Dr. Dutton lost his life by 

 accidentally becoming infected with the disease. 



It thus having been established that Heas can infect 

 man with plague, and that ticks transmit the parasites 

 of relapsing fever, it is not unreasonable to suppose 

 that other crawling Acrniin can also take their part 

 in the propagation of disease ; hence the great import- 



