506 



Tuberculosis. 



into a thick membrane covering the entire surface of the fluid. In the 

 course of time this membrane increases in thickness _ and becomes 

 crumbly. Very slight jarring of the container will cause it to break into 

 fragments causing portions to sink to the bottom of the flask where they 

 develop into globular mulberry-like white colonies. The bouillon re- 

 mains clear throughout its mass. Upon glycerin-potato medium, one of 

 the most suitable for its growth, there develop dry crumbling masses 

 which unite to form a rough irregular covering. (See Plate II.) Acid- 

 reacting brain-agar and brain-serum are also excellent media for its 

 growth. 



Arloing succeeded in producing so-called homogeneous 

 cultures by repeated shaking, in which the unusually long 

 bacilli are less acid fast than usual and motile. The origi- 

 nal potato cultures had a shiny fatty appearance. 



Morphological and Cultural Differences Observed 

 in Tubercle Bacilli of Different Origin. These were pointed 

 out by Theobald Smith in 1898. Later other investigators 

 (Kossel, Weber & Heuss) confirmed the results reported by 

 Smith. According to these investigators two types or 

 varieties of tubercle bacilli are recognized (human type and 

 bovine type). These types, however, do not include the 

 avian form of tubercle bacillus nor the varieties which 

 occur in cold blooded animals. Intermediate between the 

 human and the bovine type are observed many transition 

 forms some of which it is impossible to classify with either 

 group. The cultural characteristics, however, are cleMy. 

 manifest only when the various types are grown on the 

 same medium and under similar conditions, particularly 

 upon beef broth of amphoteric reaction with 2% glycerin. 



The bacilli of the human type, when found in morbid 

 secretions or tissues or in pure culture, are usually more 

 slender and show the irregular staining to better advantage 

 than the bacilli of the bovine type. Further, on some va- 

 rieties of potato the cultures of the human type assume a 

 dark red color in the course of three weeks ( Arpad) . They 

 also show more rapid growth in first cultures than the bacilli 

 of bovine tuberculosis. On the other hand the latter are 

 frequently characterized by their fine verrucose surface on 

 potato culture. 



The bacilli of the human type grow luxuriantly on 

 glycerin bouillon, forming a 'wrinkled membrane of even 

 thickness which spreads over the entire surface of the 

 liquid, while the bovine type forms a fine, delicate and fre- 

 quently fenestrated pellicle upon which small nodular pro- 

 tuberances develop in the course of time (Kossel, "Weber & 

 Heuss). Then again, the mulberry shaped colonies which 

 develop after inoculation of small numbers of bacilli are 

 characteristic of the bovine type. 



On bile medium or on potato impregnated with 5% 

 glycerin bile, tubercle bacilli will develop only if obtained 

 from the same species which furnished the bile. Thus the 

 human type will grow only on bile medium produced from human bile 

 and the bovine type on bovine bile, the avian type on bile obtained from 

 fowls (Calmette & Guerin). 



Fig. 80. Gly- 

 cerin agar 

 culture of the 

 tubercle ba- 

 cillus, five 

 weeks old. 



