120 MILK AND THE PUBLIC HEALTH CHAP. 



stead X. 2 would be the milk not contaminated by G. L. The 

 theory that G. L. was the fountainhead of the infection is thus in 

 perfect harmony with the fact that at farmstead X. x the farmer, 

 his wife and her sister, and the foreman milker, and at farmstead X. 9 

 the milker, and his family of eight persons, all escaped the disease ; 

 whereas the escape of all these persons is very difficult to explain, 

 if it is maintained that the cow diseases discovered at both farm- 

 steads was the source of the infection." 



The evidence that this outbreak had a bovine source really 

 rests upon the conclusions of the investigators that no human 

 source could be found, and that the infectivity of the milk was 

 coincident with the use of milk from an animal suffering from sores 

 on teats and udder similar to those found in the Hendon disease. 

 Apart from the fact that such sores and excoriations were found, 

 and that the milk of this herd was causing scarlet fever, there is 

 no evidence, clinical or bacteriological, that they were connected in 

 the relationship of cause and effect, while no evidence was adduced 

 that they might not have been there for a long time previous to 

 the outbreak. 



In view of the great difficulty in tracing the sources of isolated 

 cases of scarlet fever, it is of no particular moment that no source 

 of infection for the G. L. family could be found. 



The outbreak is an extremely interesting one in view of the 

 possibility of a bovine origin, but the evidence is, in the writer's 

 opinion, insufficient to establish that a bovine origin for the 

 epidemic was the most probable cause. 



It would appear that the evidence in favour of the existence of 

 true bovine scarlet fever is insufficient to warrant its acceptance. 



The writer l has advanced an hypothesis which, in his opinion, 

 offers the best explanation of the outbreaks of scarlet fever and 

 sore throat associated with disease of the cows. This theory is 

 that whenever the cow is a source of scarlet fever or other 

 septic disease it is because it is acting as a carrier of organisms of 

 human origin, often in a purely passive capacity, but sometimes 

 associated with active but local disease caused by the human infect- 

 ing organism. It will be seen that this hypothesis implies the 

 acceptance of two separate conclusions : 



(a) That the cow may be a source of human disease not because 

 it is constitutionally infective, but because it is acting as a carrier 

 of human pathogenic organisms. 



(b) That disease of the milk-producing organs of cows is only 

 likely to be harmful to man when the causally associated organisms 

 are of human origin, or when human organisms are superadded as 

 a secondary infection. 



1 Proceedings of Royal Society of Medicine, iv., March 1911, Epidemiological 

 Section. 



