286 BACTERIOLOGY. 



indeed, that it required the inoculation of the entire 

 contents of the body to cause tuberculosis in guinea- 

 pigs; moreover, only one or two of a litter were affected 

 at one time. According to these experiments one would 

 expect to find in man foetal or placental tubercular in- 

 fection more common than it is, whereas it is extremely 

 rare, even if the few cases reported be accepted as proven. 

 Possibly the few bacilli which may be transmitted to 

 the foetus do not find conditions favorable for their 

 development, and, being so few in number, die; or 

 they may remain latent, as has been suggested, for 

 certain lengths of time without producing visible effects, 

 and only show symptoms of infection later; but we have 

 no experimental confirmation of any such latency ex- 

 isting with regard to the tubercle bacillus, and it is not 

 to be assumed that it does exist. As to the infection of 

 the foetus from the paternal side, where the father has 

 tuberculosis of the scrotum or seminal vessels (which 

 have been found to be tuberculous in exceptional cases), 

 we have no reason to suppose that such can occur. 

 There are, however, some grounds for belief that infec- 

 tion in this way may take place from husband to wife. 

 Thus, Gartner found, as a result of his experiments in 

 animals, that a large majority of the guinea-pigs and 

 rabbits which were brought together with males whose 

 semen contained tubercle bacilli died of primary gen- 

 ital tuberculosis; but from the rarity of this affection 

 in women and cows it may be assumed that tubercle 

 bacilli occur very much less frequently in semen of men 

 and cattle than in that of the smaller animals. 



Length of Time Tubercle Bacilli Remain Virulent in 

 Sputum. Of considerable importance in studying the 

 subject of tubercular infection is the question of the 



