700 - Tujaerculosis 



specific cause of the disease, and to write so accurate a description 

 of the organism, and the lesions it produces, as to be almost without 

 a parallel in medical literature. 



Distribution.- — So far as is known, the tubercle bacillus is a 

 purely parasitic organism. It has never been found except in the 

 bodies and discharges of animals affected with tuberculosis, and 

 in dusts of which these are component parts. 



The widespread distribution of tuberculosis at one time sug- 

 gested that tubercle bacilli were ubiquitous in the atmosphere, that 

 we all inhaled them, and that it was only our vital resistance that 

 prevented us all from becoming its victims. Cornet,* however, 

 showed the bacilli to be present only in dusts with which pulverized 

 sputum was mixed, and to be most common where the greatest 

 uncleanliness prevailed. 



Fig. 276. — Tubercle bacillus in sputum (Frankel and PfeifEer). 



Morphology. — The tubercle bacillus is a slender, rod-shaped 

 organism with slightly rounded ends and a slight curve. It meas- 

 ures from 1.5 to 3.5 y. in length and from 0.2 to 0.5 n in breadth. 

 It commonly occurs in pairs, which may be associated end to end, 

 but generally overlap somewhat and are not attached to each 

 other, or in small groups in which most of the individuals have their 

 long axes in the same general direction, though one frequently 

 crosses the other at an angle. Organisms found in old pus and 

 sputum show a peculiar beaded appearance caused by fragmentation 

 of the protoplasm and the presence of metachromatic granules. 



These were thought by Koch to be spores, but are irregular in 

 shape, have ragged surfaces, are without the high refraction peculiar 

 to spores, and do not resist heat. 



The organism not infrequently presents projecting processes or 



*" Zeitschrif t fiir Hygiene," 1888, v, pp. 191-331. 



