STAINING THK SECTIONS 189 



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. 



c. Into water 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. 



