142 APPLIED BACTERIOLOGY 



the surface of a glycerine-agar plate and incubated; if 

 after twenty-one days no colonies appear, the tubercle is 

 not present. 



Some observers consider it worth while to attempt a rough 

 estimation of the number of bacilli present in sputum, with 

 a view of forming an opinion as to the rapidity with which 

 the caseous degeneration is proceeding. 



Bollinger has estimated that the daily expectorations of 

 a phthisical patient when caseation is far advanced may 

 contain twenty million bacilli. 



In cases where phthisis is suspected, an examination of 

 the sputum should always be made, particularly as phthisis, 

 when taken in time, is very amenable to treatment. In 

 examining the urine in cases of suspected tubercular aSee- 

 tion of the bladder, care must be taken in the collection 

 of the specimens to avoid contamination, as there is an 

 organism termed the Smegma bacillus, which is similar to 

 the tubercle, and behaves in the same manner to Gram's 

 stain. It is not, however, capable of growth on ordinary 

 media, and hence the application of Pastor's method as 

 described above would be conclusive. 



Occurrence and Distribution. — The disease is found all over 

 the globe, but is much more prevalent in cold and temperate 

 climates than in the tropics. The mortality due to tuber- 

 culosis is highest in March and April, and lowest in August 

 and September. 



The operatives in certain trades are especially liable to 

 be attacked by phthisis, particularly those in which there 

 is excessive moisture or gritty particles. 



The bacillus is conveyed by air, in the shape of dust ; by 

 food, such as milk, and possibly by meat. 



It has been shown that the tubercle bacillus is not 

 destroyed, if in the centre of a joint of meat over six pounds 

 in weight, by the ordinary method of cooking. 



