38 



CITY MILK SUPPLY 



uncertain; (3) physical examination; and (4) the tuberculin test. The 

 great bulk of testing is done by the last two methods. 



Physical Examination. The detection of the disease by physical 

 examination is based on the fact that as the disease progresses certain 

 symptoms become manifest to the trained observer. Of course, in time 

 these become obtrusively evident but at first they may be difficult to 

 detect as must be apparent when it is remembered that many of the organs 

 commonly attacked are impossible to get at. A persistent cough, en- 

 larged glands, tendency to be in heat frequently and alternating constipa- 

 tion and diarrhea make even the layman suspicious but these signs are 

 also symptoms of other diseases and may mislead any but the professional. 

 Moore gives the impression that physical examination is used a great deal 

 more in Europe than in the United States and that veterinarians there 

 are far more expert in this sort of diagnosis than Americans are. Some 

 hold that frequent and thorough physical examinations will keep a herd 

 free from open cases of tuberculosis and that thereby the spread of the 

 disease may be controlled, with the result that the infected market milk 

 may be kept down to a minimum quantity. 



As evidence against this contention the number of positive results 

 in the " control" samples of Sheffield, England, may be cited. Savage says 

 that samples are taken of the milk coming to the city from outsic e sources 

 and are bacteriologically examined and that when tubercle bacteria are 

 found, the farms supplying the samples are visited by a skilled veterinary 

 inspector who, in case no cows are found having tuberculosis of the udder 

 takes "control" samples to check up the work of the veterinarian. 

 Therefore, such samples are of the mixed milk of herds of cows without 

 clinical signs of tuberculosis. Table 18 shows the results of such 

 examinations. 



TABLE 18. REPORT ON 



'CONTROL" SAMPLES BY MEDICAL HEALTH OFFICERS OF 

 SHEFFIELD (SAVAGE) 



So, on an average in 16.4 per cent, of the samples, tubercle bacteria were 



