SOURCES OF HUMAN TUBERCULOSIS. 247 



Practical Conclusions. From the facts above stated 

 with regard to the conditions of growth of the tubercle 

 bacilli, their powers of resistance, and the paths by which 

 they can enter the body and produce disease (as shown by 

 experiment), the manner by which tuberculosis is naturally 

 transmitted can be readily understood. Though the ex- 

 periments of Sander show that tubercle bacilli can multiply 

 on vegetable media to a certain extent at warm summer 

 temperature, it is doubtful whether all the conditions 

 necessary for growth are provided to any extent in nature. 

 At any rate, the great multiplying ground of tubercle bacilli 

 is the animal body, and tubercular tissues and secretions 

 containing the bacilli are the chief, if not the only, means 

 by which the disease is spread. The tubercle bacilli leave 

 the body in large numbers in the sputum of phthisical 

 patients, and when the sputum becomes dried and pulverised 

 they are set free in the air. Their powers of resistance 

 in this condition have already been stated. As examples 

 of the extent to which this takes place, it may be said 

 that their presence in the air of rooms containing phthisical 

 patients has been repeatedly demonstrated. Williams 

 placed glass plates covered with glycerine in the ventilat- 

 ing shaft of the Brompton Hospital, and after five days 

 found, by microscopic examination, tubercle bacilli on the 

 surface, whilst Klein found that guinea-pigs kept in the 

 ventilating shaft became tubercular. Cornet produced 

 tuberculosis in rabbits by inoculating them with dust 

 collected from the walls of a consumptive ward. Tubercle 

 bacilli are also discharged in considerable quantities in the 

 urine in tubercular disease of the urinary tract, and also 

 by the bowel when there is tubercular ulceration, but, so 

 far as the human subject is concerned, the great means of 

 disseminating the bacilli in the outer world is dried phthisi- 

 cal sputum, and the source of danger from this means can 

 scarcely be over-estimated. Every phthisical patient ought 

 to be looked upon as a fruitful source of infection to those 

 around, and the sputum ought in every case to be collected 

 in special receptacles and thoroughly sterilised either by 



