134 STAINING. 



The most distinctive processes, involving the use of mordants and 

 regressive differentiation, can only be undertaken on sections. 

 Staining in bulk is useful when the general anatomy is the object of 

 study. For cytological work it is of little value. 



As remarked, the main object of staining is to obtain better information 

 of the appearance of the structures present in the cell. The fact, 

 however, that this appearance is not necessarily that of the living state 

 should never be allowed to escape remembrance. Without special 

 investigation of the case, it is not permissible to draw conclusions as 

 to the chemical nature of a cell constituent from its behaviour to dyes. 



212. Choice of a Stain. Mr. BOLLES LEE believes that the follow- 

 ing may be recommended to the beginner for general work : For 

 sections, MAYER'S hcemalum ; or, for chromosmium objects more 

 especially, BENDA'S or HEIDENHAIN'S iron hsematoxylin. 



For staining in toto Grenacher's alcoholic borax-carmine, or 

 Mayer's carmalum, or hsemalum, unless the object be so impermeable 

 as to require a very highly alcoholised stain, in which case take 

 Mayer's paracarmine, or for chromic acid objects Mayer's hcema- 

 calcium. 



For fresh tissues or small entire objects, methyl green, if it is not 

 important to have permanent preparations ; if it is, take carmalum 

 or alum-carmine (but both of these may give precipitates with marine 

 animals). 



