138 The Story of the Bacteria 



them to get the better of their big brother, 

 man. 



But man has more brains and has found out 

 that the weakest link in the chain of his 

 inoculation is the mosquito, and when he 

 drains the marshes in which most of the little 

 buzzing brethren breed, and screens his 

 windows against the plebeian minority to 

 whom stale water in old bottles, tin cans, 

 water butts, and puddles is birthplace, his 

 " shakes" disappear and he becomes a worth- 

 while citizen again. 



Yellow Fever 



This is a tropical disease but may flourish 

 in temperate climates in summer. It ceases 

 when the frost comes. It is certainly infec- 

 tious, it does not affect the lower animals, 

 and we do not know what living thing incites 

 it. It was formerly supposed to be contagious 

 and the infective agent carried in the clothing. 

 But through a series of brilliant recent re- 

 searches, it is now known that the yellow- 

 fever germ is carried from the sick to the well 



