Il6 ESSENTIALS OF BACTERIOLOGY 



such specimens are examined, they show tubercle bacilli alone, 

 and when inoculated in agar, give rise to pure cultures. 



Staining Bacillus Tuberculosis in Tissue (Sections). The 

 general method of Gram can be used, but the better way is to use 

 the following: 



Carbol-fuchsin, fifteen to thirty minutes. 

 5 per cent, sulphuric acid, one minute. 

 Alcohol, until a light-red tinge appears. 

 Weak methylene-blue, three to five minutes. 

 Alcohol, for a few seconds. 

 Oil of cloves, until cleared. 

 Canada balsam, to mount in. 



Instead of carbol-fuchsin, alcoholic solution of fuchsin or 

 anilin-water fuchsin can be used, but the sections must remain 

 in the stain overnight. 



Hardened Sputum and Sectioning. Sputum can be hardened 

 by placing it in 98 per cent, alcohol. Thin sections can be 

 obtained by imbedding the hardened sputum in collodion. The 

 sections are then stained as ordinary tissue sections. 



To Preserve Sputum. Sputum can be preserved for future use 

 by placing it in alcohol, where it can be kept for months. 

 Cover-glass preparations can then be made by softening the 

 coagula with a small amount of liquor potassa. 



The resisting action of the bacillus to acids is supposed 

 to be due to a peculiar arrangement of the albumin and 

 cellulose of the cell, rather than to any particular capsule 

 around it. 



Pathogenesis. When a guinea-pig has injected into its peri- 

 toneal cavity some of the diluted sputum containing tubercle 

 bacilli, it perishes in about three weeks, and the following 

 picture presents itself at the autopsy: at the point of inoculation 

 there is a local tuberculosis, little tuberculous nodules contain- 

 ing the characteristic bacilli. In the lungs and the lymphatics, 

 similar tubercles are found a general tuberculosis. 



If the animal lingers a few weeks longer, the tubercles 

 becomes necrosed in the center and degeneration occurs, the 



