582 INFECTION AND IMMUNITY. 



moist is not a source of particular danger, inas- 

 much as ordinary currents of air do not dissipate 

 it in the form of infected drops. Droplets of spu- 

 tum which are expelled by coughing contribute 

 greatly to the infected dust which surrounds a 

 patient. 



Large quantities of bacilli are often excreted in 

 the feces in intestinal tuberculosis and in the urine 

 in genitourinary tuberculosis, or in general miliary 

 tuberculosis with localization of the process in the 

 urinary organs. The pus from tuberculous ab- 

 scesses commonly is infectious. 



Human T d Great interest attaches to the possibility of infec- 

 " tion of man by the milk and meat of tuberculous 

 cattle. Previous to 1901, through the work of 

 Smith and others, the opinion had been gaining 

 ground that the bacilli of human and bovine tuber- 

 culosis are not identical. It was not always possi- 

 ble to produce tuberculosis in cattle by feeding 

 them or causing them to inhale tuberculous spu- 

 tum or pure cultures which were highly infectious 

 for other experiment animals, although bacilli of 

 bovine origin invariably caused the disease in cattle 

 when administered in a similar manner. It seemed 

 then that the two bacilli are not identical in their 

 pathogenic powers. Koch having performed such 

 experiments without being able to infect cattle with 

 bacilli of human origin expressed his belief that 

 the converse also is true, i. e.,that the bovine ba- 

 cillus is not pathogenic for man. Perhaps the 

 strongest argument in favor of this view is the 

 circumstance that primary tuberculosis of the in- 

 testines and mesenteric glands is very rare in chil- 

 dren, who drink a good deal of milk, in spite of 

 the great prevalence of tuberculous cows. Many 



