228 TUBERCUL OSIS. 



the body in large numbers in the sputum of phthisical 

 patients, and when the sputum becomes dried and pulverised 

 they become 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 stated 

 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 

 boiling or by the addition of a 5 per cent solution of 

 carbolic acid. 



Another great source of infection is almost certainly 

 the milk of cows affected with tuberculosis of the udder. 

 In such cases the presence of tubercle bacilli in the milk can 

 usually be readily detected by centrifugalising it, and then 

 examining the deposit microscopically, or by inoculating 

 an animal with it. As pointed out by Woodhead and 

 others, the milk from cows thus affected is probably the 

 great source of tabes mesenterica, which is so common in 

 young subjects. In these cases there may be tubercular 

 ulceration of the intestine, or it may be absent. Woodhead 

 found that out of 1 2 7 cases of tuberculosis in children, the 

 mesenteric glands showed tubercular affection in 100, and 



