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BACTERIOLOGICAL LABORATORY TECHNIC 



If nitrites are present a pink color is produced by these reagents. 

 Enzymes may be detected by noting whether gelatine is liquefied, 

 or milk curd digested. Both these actions are evidences of the 

 presence of enzymes. 



Bacteria growing exclusively in the absence of oxygen are 

 known as anaerobes; to cultivate these successively various forms 

 of apparatus are necessary. 



FIG. 34. A streak made in agar by a needle inoculated with aerobic bacilli 

 and then covered at one spot with cover-glass. The aerobic organisms will 

 not grow in the anaerobic conditions under the glass. (Williams.; 



The following methods are pursued in ordinary laboratory 

 manipulations : 



1. Exclusion of oxygen. 



2. Exhaustion of oxygen by means of an air-pump. 



3. Absorption of oxygen by means of chemicals that absorb 

 oxygen from the air. A mixture of pyrogallic acid and sodium 

 hydrate absorbs oxygen rapidly, leaving nitrogen only in the 

 chamber. 



