168 BACTEBIOLOGT. 



In short, the steps in the process of staining sections 

 in general are these: 



a. From alcohol into distilled water for one minute. 



b. Into the staining-fluid for from five to eight min- 

 utes. 



e. Into water for from three to five minutes. 



d. Into 0.1 per cent, acetic acid for about one-half 

 minute. 



e. Into absolute alcohol for a few seconds. 



/. Into absolute alcohol again for a few seconds. 



g. Xylol for about one-half minute. 



h. Removal with spatula or section-lifter to slide. 



i. Removal of excess of xylol. 



j. Mounting in xylol-balsam. 



The section must be lifted from one vessel to the other 

 by means of either a curved needle or a glass rod drawn 

 out to a fine end and bent in the form of a curved needle. 



By the above process of staining, which can be prac- 

 tised as a routine method for most bacteria in tissues, 

 the nuclei of the tissue cells, as well as the bacteria, will 

 be more or less deeply stained. 



Special Methods of Staining Bacteria in 

 Tissues. — For purposes of contrast-stains it sometimes 

 becomes necessary to .decolorize completely, or nearly 

 completely, the tissues and leave the bacteria unaltered 

 in color. For this purpose special methods depending 

 on the staining-peculiarities of the bacteria under con- 

 sideration have been devised. 



Gram's method with tissues. One of the most com- 

 monly employed differential stains is that of Gram. 

 In general, it is practised in the way given for its em- 

 ployment on cover-slip preparations, with some slight 

 modifications. 



