132 BACTERIOLOGY. 



Inherited Infection and Susceptibility to or Immunity 

 from Infection. The passage of bacteria from the 

 mother's blood through the placenta to the foetus has 

 been demonstrated for numerous bacteria, among the 

 most important of which may be mentioned the pneu- 

 mococcus, streptococcus, and tubercle bacillus. The 

 detection of the tubercle bacillus by Gartner and others 

 under these circumstances prevents us from denying the 

 possibility that tuberculosis developing in children may 

 have been due to infection taking place before birth. 

 The fact, however, that calves removed from tubercu- 

 lous cattle and fed on milk free from tubercle bacilli do 

 not develop tuberculosis, while those left with tubercu- 

 lous cattle become tuberculous, indicates that tubercu- 

 losis in man also is usually, at least, due to infection 

 after birth. The infection from spermatozoa is con- 

 ceivably possible in tuberculosis if the testicles are 

 affected; the same may be said of syphilis; but except 

 for syphilis, in which the nature of the infective agent 

 is unknown, we believe that such infection is, if ever 

 present, extremely rare. 



Natural immunity pertains more to species than in- 

 dividuals, and such immunity is handed down by the 

 parents to their offspring. If the immunity of one or 

 both parents has been acquired by them during their 

 lifetime previous to the birth of the offspring the im- 

 munity conferred is slight or none at all. This is espe- 

 cially true of the male side. In the case of the female 

 parent another factor comes into play after the fructi- 

 fication of the ovum viz., the absorption of products 

 from the fluids of the mother, for the placenta is no 

 barrier to soluble substances. Thus, sheep which have 

 been immunized to anthrax have moderately immune 



