ing the house were covered with fleas and he was able to bottle 1^7 

 67 in a short time. . . . As the house had a rat population only, 

 these fleas must have derived their nourishment from rats, and 

 at least one of these was plague infected. It would be simply 

 marvelous if something did not happen with the elements in 

 such favorable conjunction. 



PUBLICATION of this article on plague had preceded 

 some others, even though their work had been accom- 

 plished earlier. One [22] continued on the leprosy he had 

 unearthed in the rats. Did the house flies that fed on their open 

 lesions (or those of leprosy in human beings) sicken of their 

 bacillary soup; and were they able to carry it away to infect 

 other living objects? The bacilli, he discovered, were taken 

 into the alimentary tracts of the flies, stayed there even if the 

 flies went into pupal form. But he found also that they cleared 

 themselves of this infectious material in two or three days. 

 They did not, themselves, suffer from the disease in the in- 

 terim, nor did they remain mechanical carriers for very long. 

 Filthy business, the whole of it, but not, in the language of 

 infection, particularly dangerous. 



Until Wherry had proved that the ground squirrels, too, of 

 California, were in need of extinction, plague control had 

 centered upon the extermination of the rat. It is at once both 

 the victim of the disease and the host to its fleas. These suck 

 its blood, leaving the dead form once it has grown cold to hop 

 upon the first warm object that comes along. Thus are they 

 able, by biting, to infect it. How to kill the rat constitutes the 

 essence, therefore, of hygienic endeavor. Many schemes to 

 dispose of the rat have been tried — their trapping, their starva- 

 tion, their poisoning; their subordination to feline overlord- 

 ship. Each and all are but partially successful. Ideal would be 

 the spread of an infection among them, which while killing 

 the rat would not kill associated living forms. It had been tried 

 before. While dissecting some of his dead guinea pigs (rodents, 

 too) Wherry had unearthed an organism responsible for the 

 abscesses in their spleens and livers [24]. It was identical with 

 one that Theobald Smith had described ten years before. The 

 two had much correspondence on the subject. Wherry had 



