204 BACTERIA IN MILK AND MILK PRODUCTS 



with udder tuberculosis is greatly dependent on the extent of the dis- 

 ease in the udder. But to make the milk infective the udder must be 

 affected, and milk from such an udder possesses a considerable degree 

 of virulence. When the udder is thus itself the seat of disease, not 

 only the derived milk, but the skimmed milk, butter-milk, and even 

 butter, may all contain tuberculous material. Furthermore, tuber- 

 cular disease of the udder spreads in extent and degree with extreme 

 rapidity. From these facts it will be obvious that it is of first-rate 

 importance to be able to diagnose udder disease. This is not always 

 possible in the early stage. The signs upon which most reliance may 

 be placed are the enlargement of the lymph-glands lying above the 

 posterior region of the udder ; the serous, yellowish milk which later 

 on discharges small coagula ; the partial or total lack of milk from 

 one quarter of the udder (following upon excessive secretion) ; the 

 hard, diffuse nodular swelling and induration of a part or the whole 

 wall of the udder ; and the detection in the milk of tubercle bacilli. 

 The whole organ may increase in weight as well as size, and on post- 

 mortem examination show an increase of connective tissue, a number 

 of large nodules of tubercle, and a scattering of small granular bodies, 

 known as "miliary" tubercles. 



The udder is affected in about 2 per cent, of the cows in the 

 milking herds in this country (MacFadyean).* In London about 

 0*2 per cent, of the cows are so affected, as judged by clinical 

 observation. It will be remembered that in the country generally 

 between 20-30 per cent, of the cows suffer from tuberculosis. In 

 London 15-20 per cent, are tuberculous. The higher standard in 

 London is due to better-class animals being housed in London, to 

 more thorough inspection, and to the fact that there is no inbreeding. 

 But let us take the generally-accepted figure of 2 per cent, of the 

 cows in the United Kingdom as having tuberculous udders, and 

 therefore yielding, in greater or less degree, tuberculous milk, leaving 

 altogether out of account cows which may be tuberculous but are 

 not affected in the udder. In the United Kingdom in 1901 there 

 were 4,102,000 milch cows.f If we take 2 per cent, of these as having 

 tuberculous udders, it gives us 80,000. The average annual yield of 

 milk per cow may be taken as, at least", 400 gallons,! which means that 

 from these 80,000 tuberculous udders 32,000,000 gallons of milk are 

 obtained. It is not asserted that this large amount of milk is actually 

 virulent with tuberculous matter, but it will be admitted that the 

 entire amount of it is open to grave suspicion, if not absolute con- 

 demnation. 



* Trans, of Brit. Congress on Tuberculosis, 1902, vol. i., p. 84. 

 t In the United States of America there were in 1901, 18,112,000 railch cows in 

 actual dairy use. 



$ 420 gallons is the generally accepted figure. 



