PREVENTION OF TUBERCULOSIS 337 



In considering the value of these special powers it must 

 always be remembered that their sole object is the protection 

 of the particular city for which they were obtained. Apart 

 from any educational influence which they may exert, their 

 effect on the amount of bovine tuberculosis in the country 

 as a whole is, for practical purposes, nil as long as they are 

 only locally applied. Their national as distinct from their 

 local value is negligible. 



As regards their effectiveness to protect the community 

 obtaining the powers against the dangers of bovine tuber- 

 culosis spread by milk, the figures quoted show that, apart 

 from their initial effects, only a moderate measure of success 

 has been attained. The writer, from a careful study of the 

 results obtained, is of opinion that these clauses, confined 

 in their powers as they are by restrictions and limitations, 

 have not effected results commensurate with the cost of 

 working them. Apart from the first few years of operation, 

 when for easily understood reasons their beneficial influence 

 would be at a maximum, they do not seem to have effected 

 a marked reduction in the amount of tuberculous milk 

 imported into the cities carrying them out. 



Several considerations, apart from actual results achieved, 

 show that markedly beneficial results of a permanent 

 character are not likely to accrue. Thus a consideration of 

 the powers acquired and the clauses themselves show that 

 they are essentially based upon an assumption which cannot 

 be accepted without large reservations. The assumption is 

 that the presence of tubercle bacilli in milk is due to the 

 herd supplying the milk containing one or more cows affected 

 with clinically recognisable udder tuberculosis, and if these 

 cows are removed the danger ceases. This assumption, in 

 view of the findings of the Eoyal Commission on Tuber- 

 culosis and of other investigators, cannot be accepted as 

 true. In further support of this statement may be in- 

 stanced the facts quoted on p. 132 as to the considerable 

 number of cases in which tubercle bacilli are found in 

 milk but in which no cases of udder tuberculosis which can 

 be diagnosed are found. Apparently the cowkeeper in 

 such cases may continue to send unchecked his milk into 

 the city. 



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