CHAPTER XIV 



TUBERCULOSIS 



THE bacillus of tuberculosis, also called the tubercle 

 bacillus, was discovered by Koch in 1882. It is the cause 

 not only of " consumption" (tuberculosis of the lungs), 

 but also of all other forms of tuberculosis, such as 

 tuberculosis of bone (Pott's disease, hip-disease, white 

 swelling, cold abscess), tuberculosis of the intestines; 

 of the peritoneum, of the kidney, of the meninges, of 

 glands (scrofula), etc. The tubercle bacillus is a slender 

 rod, iojob inch long and 75^0 inch thick. It is strictly 

 aerobic, grows only on special media, and then but 

 slowly, is not motile, and does not produce spores. It 

 stains with difficulty, but, once stained, resists decolor- 

 ization with acids. It is, therefore, spoken of as an 

 "acid-fast" bacillus. (See Plate I.) 



Tuberculosis is an extremely common disease in man, 

 and causes about one-eighth of all deaths. The disease 

 is also very prevalent among cows, and hence tubercle 

 bacilli are often found in cows' milk. The tubercle 

 bacilli from this source differ somewhat from those 

 found in human pulmonary tuberculosis, and until 

 recently there was considerable controversy regarding 

 the role of bovine tuberculosis in the spread of tuber- 

 culosis in man. It is now established that while pul- 

 monary tuberculosis is practically always caused by 

 bacilli of human origin, certain other tuberculous in- 



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