THE GROWTH OF GROUPS 37 



organized, under the direction of the Government of 

 India. This was conducted not only in plague-stricken 

 towns and villages, but also in places which had been 

 free from the disease since the commencement of the 

 present epidemic. These measures were of course in 

 addition to the more usual methods of combating disease, 

 such as segregation, quarantine and inoculation. Apart 

 from their influence on the epidemic, the measures against 

 rats afforded an opportunity of examining these animals 

 from a general point of view. Any kind of knowledge was 

 required, which might help in determining the best means 

 of combating the disease. The writer was appointed for 

 a period of eighteen months to carry on a general inquiry 

 of this kind. The detailed results of the inquiry have 

 already been published in the records of the Indian 

 Museum. In their bearing upon sanitation they are 

 not of direct importance, but during the progress of the 

 inquiry some useful information concerning evolution 

 was gained. It is necessary to emphasize that the 

 investigation was made primarily in order to increase our 

 knowledge of the natural history of disease. The facts 

 relating to evolution forced themselves into notice in 

 spite of this. The facts appear to be few and incomplete, 

 but similar ones will seldom be obtained. The oppor- 

 tunity afforded by the exterminatory measures was most 

 unusual, since these were conducted on a very large 

 scale. It is unlikely that such action would have been 

 taken solely in the interests of biology. Although the 

 facts to be related have had a decided influence on my 

 own opinion, yet they are too incomplete to be put forward 

 as proving anything, i.e. supposing that propositions 

 relating to evolution are capable of proof. Many doubtful 



