TUBERCULOSIS. 



*93 



While the great men of the early days of pathology 

 clearly saw that the time must come when the parasitic 

 nature of this disease would be proved, and some, as 

 Klebs, Villemin, and Cohnheim, were "within an ace " 

 of the discovery, it remained for Robert Koch to succeed 

 in demonstrating and isolating the specific bacillus, now 

 so well known, and to write so accurate a description of 

 the organism and the lesions it produces as to render it 

 almost unparalleled in medical literature. 



The tubercle bacillus (Fig. 64) is a rod-shaped organ- 



Fig. 64. — Section of a peritoneal tubercle from a cow, showing the tubercle 

 bacilli; x 500 (Frankel and Pfeiffer). 



ism with rounded ends and a slight curve, measuring 

 from 1.5-3.5 t 1 * n length and from 0.2-0.5 // m breadth. 

 It very commonly occurs in pairs, which may be asso- 

 ciated end to end, but generally overlap somewhat and 

 are not attached to each other. In organisms found in 

 pus and sputum a peculiar beaded appearance is very 

 common (Fig. 65). By some these fragmentations are 

 thought to be bacilli in the stage of sporulation (see Fig. 

 66). Koch originally held this view himself, but re- 

 searches have not been able to substantiate the opinion. 



