140 CHAPTER xr. 



frequently indicated, both on account of its greater power of 

 penetration and as being less injurious to tissues. It is a 

 good rule not to let staining baths contain more than fifty 

 per cent, of alcohol. 



Better results (as regards the quality of the stain, not as 

 regards the preservation of the tissues) are generally obtained 

 by prolonged staining in very dilute solutions, rather than 

 by a short bath in a strong one. 



210. Choice of a Stain. The following may be recommended 

 to the beginner for general work: For sections. MAYER'S 

 Jisemalum or, for chroniosmium objects more especially, 

 BENDA'S or HEIDENHAIN'S iron hasmatoxylin. 



For staining in toto Grenadier's alcoholic borax -car mine, 

 or Mayer's carmalnm, or hamialum, 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 hsemacalcium. 



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). 



Most of the carmine and haematoxylin solutions, properly 

 used, give stains that are indefinitely permanent at least 

 in balsam. But most of the stains obtained with coal-tar 

 dyes fade much in a few months or years. The most 

 permanent are safranin, gentian violet, Bismark brown, and 

 picric acid, which fade very little. Victoria blue, I find, is 

 also fairly permanent. 



