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 numbers 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. 



