94 THE MILK QUESTION 



localized in the lymphatic glands (scrofula) and usually 

 terminates favorably. On the other hand, the human 

 bacillus is very prone to attack the lungs and cause pul- 

 monary tuberculosis, which is the common fatal type in 

 man. This, however, is not always the case. While the 

 bovine bacillus is not known to attack the lungs in man it 

 may attack the coverings of the brain, causing tuberculous 

 meningitis, the peritoneum, causing tuberculous periton- 

 itis, or other vital structures, resulting in death. Bo- 

 vine tuberculosis may also become generalized, resulting 

 in acute miliary tuberculosis or "galloping consump- 

 tion." 



The differences which the bacteriologist depends upon to 

 distinguish a bovine bacillus from a human bacillus are 

 based upon animal experimentation and cultural characters. 

 Thus, when even large numbers of the human variety are 

 injected into a caK a general disease does not result: at 

 most there is only a local lesion. On the other hand, calves 

 are very susceptible to injections of bovine cultures. A 

 small quantity (0.001 gram of pure culture) of a bovine 

 strain injected subcutaneously into a rabbit is suflBcient to 

 cause generalized tuberculosis and death of the animal in 

 about six weeks. Ten times this amount of a human strain 

 produces at most a slight localized tuberculosis. The hu- 

 man bacillus grows well upon artificial culture media, 

 covering the entire surface of the medium with a rich, dry, 

 crinkled, mould-like vegetation. The growth of the bovine 

 bacillus upon artificial culture media is more sparse, thinner, 

 less extensive, and somewhat slower. The human bacillus 

 usually produces more acid in artificial culture media, with 

 a different reaction curve from the bovine bacillus. The 

 two types cannot be distinguished from each other under 

 the microscope, although the human bacillus is frequently 

 longer, club-shaped, and stains intermittently, while the 

 bovine type is often shorter, straighter, more regular, and 

 stains solidly. 



