288 TUBERCULOSIS 



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. 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 glycerin in the 

 ventilating shaft of the firompton 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 con- 

 sumptive ward. Tubercle bacilli are also discharged in consider- 

 able 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 phthisical 

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

 be overestimated. Every phthisical patient ought to be looked 

 upon as a fruitful source of infection to those around, and should 

 only expectorate on pieces of rag which are afterwards to be 

 burnt, or into special receptacles which are then to be sterilised 

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

 carbolic acid. 



Another great source of infection is the milk of cows affected 

 with tuberculosis of the udder, and this is responsible for a 

 considerable proportion of tuberculosis of lymphatic glands, 

 bones, and joints, etc., in young children, as above detailed. 

 In the examination of milk, animal inoculation with centri- 

 fugalised samples is the only reliable means of detecting the 

 presence of tubercle bacilli. 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 (vide p. 281). In these cases there may be tubercular 

 ulceration of the intestine, or it may be absent. It is especially 

 in children that this mode of infection occurs, as in the adult 

 ulceration of the intestine is rare as a primary infection, though 

 it is common in phthisical patients as the result of infection by 

 the bacilli in the sputum which has been swallowed. There is 



