BACTERIA AND DISEASE 269 



following is not an unlikely series of events terminating in 

 consumption (tuberculosis of the lungs) : (a) The individual 

 is predisposed by inheritance to tuberculosis ; (b) an ordinary 

 chronic catarrh, which lowers the resisting power of the 

 lungs, may be contracted; (c) the epithelial collections in 

 the air vesicles of the lung i. e., dead matter attached to 

 the body afford an excellent nidus for bacteria; (d) owing 

 to occupation, or personal habits, or surroundings, the 

 patient comes within a range of tubercular infection, and 

 the specific bacilli of tubercle gain access to the lungs. The 

 result, it is needless to state, will be a case of consumption 

 more or less acute according to environment and treatment. 

 The channels of infection by which organisms gain the 

 vantage-ground afforded by the depressed tissues are various, 

 and next to the maintenance of resistant tissues they call for 

 most attention from the physician and surgeon. It is in 

 this field of preventive medicine that is to say, preventing 

 infective matter from ever entering the tissues at all that 

 science has triumphed in recent years. It is, in short, ap- 

 plied bacteriology, and therefore claims consideration in this 

 place. 



1. Pure Heredity. By this term may be understood the 

 actual transmission from the mother to the unborn child of 

 the specific virus of the disease. That such a conveyance 

 may occur is generally admitted by pathologists, but it is 

 impossible to enter fully into the matter in such a book as 

 the present. Summarily we may say that, though this sort 

 of transmission is possible, it is not frequent, nor is disease 

 appreciably spread through such a channel. Sixty per cent, 

 of consumptives, it has been estimated, have tuberculous 

 progenitors, and this is the highest figure. Many would be 

 justified from experience in placing it at half that number. 



2. Inoculation, or inserting virus through a broken surface 

 of skin, is itself a sufficiently obvious mode of infection to 

 call for little comment. Yet it is under this heading that 



