132 MILK AND THE PUBLIC HEALTH chap. 



The results in other areas with similar legal powers are not 

 nearly so favourable. In particular the Sheffield results may 

 be quoted. In connection with the Sheffield milk clauses, 

 samples have been taken for a number of years from milk 

 reaching the city from outside areas. These are bacterio- 

 logically examined, and when tubercle bacilli are found the 

 farms supplying the particular milk samples are visited by a 

 skilled veterinary inspector. When in following up such 

 positive samples no cows can be found exhibiting signs of 

 tuberculosis of the udder, what is called a control sample is 

 taken to check the veterinary examination. Such samples are 

 therefore samples of the mixed milk of herds of cows without 

 clinical signs of tuberculosis. The number taken and results 

 of the examinations were as follows : 



In other words, in 16 4 per cent of cases, on an average, 

 tubercle bacilli were found in milk produced by cows passed 

 by a skilled veterinary inspector specially on the look-out for 

 the condition as free from udder tuberculosis. It is not 

 possible to say what proportion of this was due to early and 

 unrecognisable udder tuberculosis. 



Dr. Eenney ^ writes me that, as regards Sunderland, in 

 quite a large proportion of cases the cows from farms supplying 

 tuberculous milk appear to be in first-class condition, and it 

 was not possible to single out any particular cow which was 

 likely to be affected with the disease. 



> Report of Medical Officer of Health, Sheffield, 1909, p^j. 46-47. 

 ^ Personal comimmicatiou to the writer. 



