284 BACTERIOLOGY. 
the flesh of tuberculous cattle. Here the same condi- 
tions hold good as in the infection by milk, only the 
danger is considerably less, from the fact that meat is 
usually cooked, and also because the muscular tissues 
are seldom attacked. In view of the great mortality 
from tubercular diseases among mankind, the legisla- 
tive control and inspection of cattle and milk would 
seem to be an absolute necessity. Asa practical and 
simple method of preventing infection, especially 
among children, the sterilization (by heat) of the milk 
used as food must commend itself toall. Itis only right 
to state, however, that the actual proof that human tuber- 
culosis has come from milk or food infected with bovine 
tuberculosis is very small, and that it is perfectly pos- 
sible that the bovine bacilli may not be as virulent for 
man as for animals, still we know that human tubercu- 
losis produces bovine tuberculosis in young and suscep- 
tible animals, and the reverse is in all probability true. 
The relation of bovine to human tubercle bacilli will 
be discussed later in this chapter. 
Auto-infection by Swallowing Sputum. The secondary 
forms of tuberculosis which often succeed a primary 
infection of the lungs may be explained as an auto- 
infection from the swallowing of sputum containing 
bacilli, these passing through the gastric juice unaf- 
fected. It is a wonder, indeed, that intestinal tuber- 
culosis is not more common than it is in consumption; 
but this is probably due to the fact that in adults the 
intestines are comparatively insusceptible. Tubercu- 
losis may also begin as a local infection in the lungs or 
intestines, and thence extend to other parts of the body, 
until, passing into the circulation, a general miliary 
tuberculosis results. 
