ACUTE INFECTIOUS DISEASES 



99 



about three and a half times as much as males, and adults furnished 

 three times as many cases as children. The incubation period was 

 apparently not longer than two days. The evidence implicating 

 a particular milkman's (M.) milk was complete, being derived from 

 information supplied by medical men and from house-to-house 

 inquiries. The following table shows the relationship of the cases 

 attended by medical men, for which particulars were available, and 

 the milk supply : 



The outbreak was nearly confined to the west side, an area not 

 including more than 20 to 25 per cent of the population. The 

 house-to-house inquiries made in four selected areas showed that 

 60'9 per cent of the houses supplied by M.'s milk were invaded, 

 as compared with 6 per cent for the other milk vendors. The 

 milkman M. obtained his milk from six farms, and from a 

 study of the distribution of the milk to the different milk rounds, 

 and the different incidence of the disease on the different rounds, 

 it was possible to point to farm B as the offending source of supply. 

 All the farms were inspected, but only on farm B were human cases 

 of illness or disease amongst the cows met with. Upon this farm 

 a cow was found, in a shed with the others, suffering from mastitis 

 of one quarter, and which had been noticed to be ill since about 

 April 19. The milk of this cow was being added to the milk 

 up to the time of visit, April 27. The cessation of the outbreak 

 corresponded with the exclusion of the milk of this particular cow. 

 Several cases of illness were found on the farm, but the cases were 

 coincident with cases in the town. The first illness on the farm 

 was that of the farmer himself, who suffered from a severe sore 

 throat, which confined him to bed for three or four days. He 

 never milked the cows, and said he had very little to do with them. 

 The onset of his illness was April 17, a date which coincided with 

 other cases in the town. This with other facts renders it nearly 

 certain that he was infected from the milk and was not the source 

 of infection of the milk. Five or six other cases occurred amongst 

 the farmer's family on the farm, but all began after April 20, 

 and all drank the milk. The outbreak started about April 17 



