SUNSHINE AND LIFE 87 



increases or reduces an animal's susceptibility to 

 particular diseases, those selected for investigation 

 being typhoid fever and cholera. For this purpose 

 guinea-pigs were exposed to the full rays of the 

 sun during a period of from nine to fifteen hours 

 for two days, whilst other guinea-pigs, for the 

 sake of comparison, were not permitted to have 

 more light than that obtainable in a stable where 

 only diffused light was admitted. Both these 

 sets of animals were subsequently infected with 

 virulent cultures of cholera and typhoid germs 

 respectively, and were in neither case exposed 

 to sunshine. The results which Dr. Masella 

 obtained were remarkable, for he found that 

 those animals which previous to infection had 

 been placed in the sunshine died more rapidly 

 than those which had been kept in the stable, 

 and that the exposure to the sun's rays had so 

 increased their susceptibility to these diseases 

 that they succumbed to smaller doses, and doses, 

 moreover, which did not prove fatal to the other 

 guinea-pigs. Still more striking was the part 

 played by insolation in the course of these 

 diseases in animals exposed to sunshine after 

 inoculation, for instead of dying in from fifteen 

 to twenty -four hours, they succumbed in from 

 three to five hours. 



Here, then, we find sunshine, in some mysteri- 



