ESSENTIALS OF BACTERIOLOGY 



albumin, and the ash shows a large amount of phosphoric 

 acid. Indol not found. 



Staining. The tubercle bacilli require special methods to 

 stain them, and a great number have been introduced. They 

 are stained with great difficulty, but once stained, they are 

 very resistant to decolorizing agents, hence called acid-proof 

 or acid-fast. Upon these facts all 

 the methods are founded. 



The resisting action of the bacil- 

 lus to acids is supposed to be due 

 to a peculiar arrangement of the 

 albumin and cellulose of the cell, 

 rather than to any particular cap- 

 sule around it. A waxy substance, 

 made up of fatty acid, has been 

 found and supposed to account for 

 this resistance. Others believe this 

 substance to be an alcohol. 



It will be necessary to describe 

 only those methods principally in 

 use; and as the examination of 

 sputum for bacilli is of so frequent 

 an occurrence and so necessary, it 

 is well to detail in particular the 

 method of staining. 



Starting with the sputum, we 

 search for little clumps or rolled-up 

 masses; if these are not present, 

 the most solid portions of the 

 mucus are brought with forceps 

 upon a clean cover-glass; very little 

 suffices. With another cover-glass 



the mass is pressed and spread out evenly. Drawing one glass 

 over the other, we obtain two specimens, and these are put 

 aside or held high over the flame until dry. 



When the preparation is dry and has been fixed by passing 

 through the flame three times, carbolfuchsin is dropped on 



Fig. 50. Bacillus tuber- 

 culosis; glycerin agar-agar 

 culture, several months old 

 (Curtis). 



