50 



solvent by alcohol, and usually remove the alcohol with water. In 

 the case of celloidin sections the first step is unnecessary. If the 

 tissue was hardened and cut in alcohol, the second step may likewise 

 be omitted. 



142. In toto Staining. If the staining has already been 

 done, ( 79) these "preliminary steps" are of course all unnecessary, 

 save the removal of the paraffin by xylene. 



143. Xylene. Leave paraffin sections in xylene until the 

 paraffin is entirely dissolved out, requiring usually only a few seconds. 

 A longer stay generally does no harm. 



144. Alcohol. Transfer paraffin sections from xylene to 

 95% alcohol leaving the sections in the alcohol 5 to 10 minutes; or 

 if you wish, shorten the period to a minute or so by waving the slide 

 gently to and fro in the alcohol. 



Celloidin sections cut by the clarification method, are placed 

 in alcohol to remove the clarifier. This may take a longer time, and 

 if there are many slides it is well to use two changes of alcohol. A 

 longer stay in alcohol does no harm. 



145. Water. Remove the 95% alcohol with water if the 

 stain is an aqueous one. 



146. Staining. The following schema shows the general 

 steps in staining and mounting. In all the processes, seemingly 

 complicated, if it is remembered that the succession of media as in 

 histological technique generally depends upon their miscibility or 

 some special reaction, and the reason for the various steps is recog- 

 nized, much of the difficulty in remembering the order in which 

 they come will be avoided. 



