PATHOGENIC BACTERIA. 105 



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 tubercular 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 constitu- 

 ting the cause in ^ 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 would 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, 

 made public in his address to the Tuberculosis Congress in 

 1901, that human and bovine tuberculosis are distinct and that 

 infection of human beings from cattle occurs so seldom that no 

 general regulations to restrict it are necessary, has found few 

 adherents. It is true that certain differences exist between 

 human and bovine tubercle bacilli, the latter appearing to be 

 more virulent to animals, and it is a fact that cattle are very 



