IMMUNITY. 117 
the finding of tubercle bacilli in milk when the gland 
itself was intact and the animal tubercular. Some 
authorities have put its presence in milk, under these 
circumstances, as high as 50 per cent. of the cases. 
This, in our experience, is undoubtedly too high, and 
probably these observers have been deceived by the 
pseudo-tubercle bacilli. They are undoubtedly pres- 
ent, however, in the milk of some animals in which 
tubercular disease of the gland could not be demon- 
strated. The finding of streptococci and staphylococci 
is due probably in the majority of cases to the infections 
taking place as the milk is voided, for the epithelium 
at the outlet of the lacteal ducts is always infected with 
staphylococci, and usually streptococci, which have often 
been received from the mouth of the sucking infant. 
Whether bacteria are eliminated from the blood by 
the sweat is a mooted point. The skin is always the 
seat of the staphylococcus and frequently of other bac- 
teria, so that it is difficult to determine in any given 
case the origin of the bacteria found in the sweat. 
Many observers have reported the passage of bacteria 
from the blood through the mucous membrane. So 
long as the organs of secretion are not injured it is not 
likely that many micro-organisms are eliminated from 
the blood in this way. Bacteria are sometimes elimi- 
nated through the urine, but here, as a rule, when 
great pumbers of organisms are found, it is due to 
development in the bladder. Such removal, moreover, 
has little if any beneficial effect; but, on the other hand, 
may be a source of danger to others, as in typhoid 
fever. The removal of the poisonous products of bac- 
teria by the kidneys, intestines, etc., on the contrary, 
is of great advantage to the organism. 
