TUBERCULOSIS. 357 



cavity and infect all the discharges from the mouth and nose. 

 It is true that the cow does not expectorate, but by putting 

 her nose in the drinking trough she will be sure to contaminate 

 the drinking water, and when she licks another animal, as she 

 will be sure to do if she stands near others, she will leave 

 some of the bacilli clinging to the second individual, ready to 

 begin their mischief if they chance to get carried to a suscep- 

 tible part, as they are very likely to do by being swallowed. 

 Moreover, although the cow does not expectorate, she does 

 swallow all of the secretions from her mouth. The tubercle 

 bacilli will thus be carried to the stomach, and through the 

 intestine, from whence, if not destroyed by the digestive juices, 

 they will be voided with the excrement. If the disease is 

 located in the intestine the bacilli will be sure to be discharged 

 with the excrement. In these ways the excrement of tuber- 

 culous cattle is sure to be impregnated with the bacilli. Now 

 the conditions of the ordinary cow stall, in even the best cow 

 barn, are such as to make it almost inevitable that the infec- 

 tious material will soon be distributed through the whole barn. 

 The excrement is carried over the floor, perhaps, for some dis- 

 tance to the opening used for its exit, and the farmer's boots 

 will always collect more or less of this excrement and carry it 

 through the barn. The particles adhering to his boots will be 

 sure to be knocked off when dry, and will thus be carried every- 

 where that the farmer goes. They will be certain to be 

 dislodged near a healthy cow and will, most likely, become 

 mixed with her food which is commonly thrown on the floor 

 in front of her. If not in the food the particles will eventually 

 become dry and be distributed through the barn as dust. In 

 short it is inevitable that the bacilli voided with the excrement 

 will, in time, get an opportunity to come in contact with every 

 healthy animal kept in the same barn. These facts are quite 

 sufficient to account for the spread of the disease from animal 

 to animal in the same barn, under the ordinary conditions. 



