PATHOGENIC BACTERIA 1IJ 



periphery still containing active bacilli, cavities having formed 

 in the center. 



Since the bacilli die in course of time, killed by their own 

 products, their number forms no correct guide of the dam- 

 age present: even their absence in the sputum does not preclude 

 the absence of a tuberculous process. // is their presence only 

 that warrants a positive declaration. The number of bacilli in 

 a given specimen is no indication of the severity of the disease. 



They are found in the blood only when a vessel has come in 

 direct contact with a tuberculous process through rupture or 

 otherwise. They have been found in other secretions milk, 

 urine, etc. 



Man is infected as follows: 



Through Wounds. Local tuberculosis. 



Through Nutrition. Milk and meat of tuberculous animals. 

 Phthisical patients swallowing their own sputum and causing 

 an intestinal tuberculosis. 



Inhalation. This is the most usual way, probably constitut- 

 ing the cause in nine-tenths of the cases, except in children. 



The sputum of phthisical patients expectorated on the floors 

 of dwelling-houses, in handkerchiefs, etc., dries, and the bacilli 

 set free are placed in motion by the wind, or rising with the dust, 

 are thus inhaled by those present. When the sputum is kept 

 from drying by expectoration in vessels containing water, this 

 great danger can be avoided. 



Nearly all the cases of heredity can be explained in this man- 

 ner; the young children, possessing very little resistance, are 

 constantly exposed to the infection through inhalation, and are 

 especially prone to intestinal infection through milk and other 

 foods. 



Immunity. No one can be said to be immune, though per- 

 sons who have been greatly weakened offer less resistance than 

 healthy individuals. 



Tuberculosis in Animals. Tuberculosis is probably the most 

 widely disseminated disease among domestic animals, and 

 affects cattle, pigs, horses, dogs, cats, the smaller ruminants, 

 birds, and even turtles and fish. The conclusion of Koch, 



