84 MILK HYGIENE 



amined in the usual way with an immersion lens and 

 Abbe condenser. The tubercle bacilli are colored red, 

 other bacteria and the rest of the preparation are 

 colored blue. 



So-called " acid-fast "' bacilli may occur in milk 

 and butter as well as in the excrement of the cow. These 

 bacilli, which by the above methods are also colored red, 

 are difficult to distinguish with certainty from the real 

 tubercle bacilli, even by microscopic examination, al- 

 though they are usually thicker and shorter. Unfortu- 

 nately, we know but little of the conditions governing 

 their occurrence in milk. There is reason to believe that 

 they usually occur as a result of accidental contamina- 

 tion after the milk is drawn. In order that one may 

 be quite safe in his conclusions from this examina- 

 tion, and be able to avoid confusing the acid-fast and 

 tubercle bacilli, the udder secretion or the discharge 

 from the uterus that is to be examined microscopically 

 must be taken as pure as possible in a clean tube and, if 

 the examination cannot be made at once, an antiseptic (a 

 little ether or chloroform, a few drops of formalin) 

 should be added. Acid-fast bacilli accidentally added, 

 will not increase under these conditions, and their num- 

 ber will always be so small that they can hardly be de- 

 tected. It is, however, not wholly disproven that such 

 bacilli may appear in the milk before it is drawn. De 

 Jong has reported a case of mastitis caused by acid-fast 

 bacilli, but this is the only case of the sort reported up 

 to this time. From knowledge gained during the last 

 four or five years in the experimental laboratory of 

 Copenhagen from investigations of milk samples and 

 the control of the diagnosis of udder tuberculosis from 

 small samples of tissue from condemned and slaughtered 

 cows, it follows that errors very seldom occur as a result 

 of confusing these organisms. 



