lo Bulletin 150. 



circumcision ; or in inserting earrings formerly used by tubercu- 

 lous persons ; or in inhaling the infecting dust through a nose 

 excoriated by a catarrh ; or in handling infected carcasses in the 

 butcher's shops ; or finally through mouth or throat abrasions 

 caused b}' hard indigestiVjle materials. 



4. Through the inammary glands . This gland is especially sub- 

 ject to wounds by the horns and to sores and abrasions in connec- 

 tion with milking which form entrance-channels for the bacilli 

 present in the dust of the barn. The opening of the teat is also 

 a door of entry through which the germ may invade the milk 

 ducts and glandular tissue. It is not to be forgotten, however, 

 that the milk gland is especially liable to become infected 

 through the blood which is sent in such enormous quantities 

 through its tissues, and is liable to implant any bacilli which may 

 have entered the blood stream. The gland is, therefore, espe- 

 cially liable to infection from without and within and once infected 

 is a source of the greatest danger to the milk consumer. 



5. Through sex2ial congress. In cows the generative organs 

 are often the seat of tuberculosis inducing nymphomania or ster- 

 ility, and the disease has been repeatedly produced experimen- 

 tally by smearing the infecting matter on the penis or introduc- 

 ing it into the vagina. The bacillus has even been found in the 

 semen of an infected male so that transmission by this channel 

 to the female can be easily understood. x\ll this has a very direct 

 bearing upon the question of the propriety of using the same 

 sire on the tuberculous and sound, and of the admission of 

 females from tuberculous herds to be served by the sires in sound 



ones. 



6. Through heredity. Hereditarj^ transmission of tuberculosis 

 has long been recognized, and until recently accorded a role 

 much more important than its infrequency would warrant. 

 Various conditions militate against its occurrence ; the foetus 

 is essential^ a carnivorous animal, living on the secretions of 

 the dam and not on the direct products of the vegetable king- 

 dom. It has, therefore, that measure of resistance which 

 inheres in the flesh feeding as compared with the vegetable feed- 

 ing animal. It may be infected through the semen of the sire, 

 but the rule appears to be that the ovum thus early affected rarely 



