120 PASTEUR AND AFTER PASTEUR 



to tell who they were or where they came from, 

 mothers lying cold with helpless babies beside them 

 whom no one dared pick up to take care of. ... 

 Thousands of pounds were wasted on disinfectants, 

 which experiment has since shown are utterly use- 

 less, and innumerable lives were lost through 

 ignorance of the proper precautions to adopt. . . . 

 It was only after years of observation and of 

 laboratory experiments that it was discovered how 

 plague really spreads. 



" As time went on, and epidemic succeeded 

 epidemic, it gradually came to be realised that the 

 principal agent in the start and spread of plague 

 among men was the rat. No rats, no plague, passed 

 into a sanitary byword, and the common people 

 came to regard dead rats as a species of omen, and 

 a warning to quit the houses where they were 

 discovered. . . . 



" The Plague Commission, sent out from England 

 in 1898 at the request of the Indian Government, 

 came to the conclusion that the infection of plague 

 always entered through the skin. 



" About the same time, a French observer made 

 experiments which tended to incriminate the flea, 

 though the results of his researches were by no 

 means conclusive. A young officer of the Indian 

 Medical Service was, however, so convinced, by a 

 study of the facts brought to light by the ex- 

 periences of successive epidemics, that there was 

 something in this theory, that he proceeded to study 

 the rats of Bombay, and the insects parasitic upon 

 them. He discovered that the flea found on rats 

 is of a different species from that infecting man ; 

 but that if the rats were removed by disease or 

 otherwise, their fleas would take to man and feed 



