132 BULI^ETIN 65. 



along with half as many deaths from other causes this would kill 

 the whole 1,200 in 16 years- 



These are extreme examples it is true, in which the transmission 

 and fostering of the disease by cattle, is extended and aggravated 

 b}^ overcrowding and every imaginable unhygienic condition, 

 among the human consumers. 



Experhnental Tuberculosis by Feedmg. 



The experimental transmission of tuberculosis by feeding 

 tuburculous products was demonstrated by Villemin, Giinther 

 and Harms, Zurn, Gerlach, Johne, Kolb, Toussaint, Chauvean, 

 Peuch, Leisering, Bollinger and a host of others, the animals in- 

 fected in this way including Guinea pigs, rabbits, fowls, swine, 

 sheep, goats, dogs, cats and birds. Infection was by no means so 

 constant as when inoculation was performed, yet in 322 experi- 

 ments recorded by Johne 13 per cent, became tuberculous. The 

 varying results depend on a variety of causes, among which may 

 be named : — 



ist. The relative susceptibility of the various animals experi- 

 mented on. As we know this varies greatly with the genus, 

 species, family and even the individual. 



2d. The condition of the digestive organs at the time of feed- 

 ing. The bacillus tuberculosis lives in an alkaline or neutral 

 medium and suffers weaking or even death in an acid liquid like 

 the contents of the stomach during active digestion. If there- 

 fore the subject of experiment has a strong digestion, and if in- 

 fecting matter is taken only during active digestion, infection is 

 usually promoted. If on the other hand the infecting material 

 passes through the stomach in water or otherwise in the intervals 

 between digestion when the stomach is neutral, if there is indi- 

 gestion so that the contents are only mildly acid, and infecting 

 morsels pass into the bowel without having been digested or 

 thoroughly impregnated with acid, or if the stomach is overloaded 

 so that part of its food passes on undigested, then manifestly in- 

 fection is possible or probable. Again if there are raw sores on the 

 mouth, throat or gullet or if the germ happens to lodge in the 

 recesses of the bowels or pass down into the lungs infection may 

 start from any such point as a center. 



3d. The germ is more or less virulent according to the animal 



