MILK-BORNE TUBERCULOSIS 



205 



There are a variety of conditions in addition to the vera causa, the 

 presence of the bacillus of tubercle, which make the disease common 

 amongst cattle. Constitution, temperament, age, work, food, in- 

 breeding, and prolonged lactation, are the individual features which 

 act as predisposing conditions ; they may act by favouring the pro- 

 pagation of the bacUlus or by weakening the resistance of the tissues. 

 To this category must further be added conditions of environment. 

 Bad stabling, dark, ill-ventilated stalls, high temperature, prolonged 

 and close contact with other cows, all tend in the same direction. 



The danger from drinking raw tuberculous milk only exists for 

 persons who use it as their sole or priacipal food, that is to say, young 

 children and certain invalids. With adults in normal health, the 

 danger is greatly minimised, as the healthy digestive tract is relatively 

 insusceptible. Moreover, dairy milk is almost invariably mixed milk ; 

 that is to say, that if there is a tubercular cow in a herd yielding tubercle 

 bacilli in her mUk, the addition of the milk of the rest of the herd so 

 effectually dilutes the whole as to render it in some degree innocuous. 



It should not be forgotten that milk may become tubercular 

 through the carelessness or dirty habits of the milker. Such a 

 common practice as moistening the hands with saKva previously to 

 milking may, in cases of tubercular milkers, effectually contaminate 

 the milk. Again, it may become polluted by dried tubercular matter 

 gettmg into it from dust or infected dried excreta. Such convey- 

 ances must be of rare occurrence, yet their possibility should not be 

 forgotten. 



The Tubercle Bacillus in Market Milk. — Investigations have been 

 made in many cities as to the actual occurrence of the tubercle 



Table skoicing ike Total Number q/' Milks Examined Bacteriological ly for 



Tubercle Bacilli from August 1896 to Z\st December 1903. 



(Liverpool.) 



bacillus in milk as placed on the market. It has been found in 



