BACTERIACE.E : THE TUBERCLE BACILLUS 



303 



acid (PC>4). The waxy constituent of 

 the bacterial cells is of particular in- 

 terest. This makes up from 8 to 40 per 

 cent of the dry substance, less in young 

 and more in old cultures. The acid-proof 

 staining property depends upon this 

 waxy substance, for the bacilli from 

 which it has been extracted by ether-al- 

 cohol are no longer acid-proof while the 

 wax itself exhibits this peculiarity of 

 staining. It is also known that the ba- 

 cilli in young cultures are on the whole 

 less acid-proof than those from old cul- 

 tures in which chemical analysis shows 

 a greater concentration of the waxy sub- 

 stance. The protein substances, largely 

 nuclein, make up about 25 per cent of 

 the dry cell substance. Several other 

 constituents of the cell have been iden- 

 tified. As in the case of other bacteria 

 the chemical composition varies within 

 rather wide limits according to the nutri- 

 tive medium, conditions of growth and 

 especially the age of the culture. 



The poisons of the tubercle bacillus 

 exist to a large extent in an inactive 

 form in the culture fluid and more 

 particularly as an undissolved constituent 

 of the bacterial cell bodies. Culture fil- 

 trates exert little or no effect upon in- 

 jection into normal animals. The dead 



FIG. 128 Bacillus tuber- 



bacilli, however, give rise to local mflam- culosis. Culture on glycerin 

 mation and in many instances stimulate agar several month 

 the formation of typical tubercles at the 

 point where they lodge. Evidently the 



(From McFarla nd after 

 Curtis.) 



