12 THE CELL [CH. i 



a suitable mixture of differently coloured acid and basic 

 stains is used, or if the section is treated with one in succes- 

 sion to the other, it is often possible to get very sharp 

 differentiation of the various constituents of the cell. 

 Structures which take acid stains are spoken of as oxyphil, 

 those which take basic stains as basiphil. In addition to the 

 stains which are more or less specific for chromatin, but 

 which are also taken up by certain other structures, various 

 special stains are used for particular purposes, e.g. to indi- 

 cate the presence of fat or other inclusions or secretions of 

 the cytoplasm. Since, however, comparatively few stains 

 are absolutely specific, it is advisable in most cases to test 

 any doubtful body with more than one; otherwise it may 

 happen that, for example, a body is identified as consisting 

 of chromatin, when it is really an inclusion of some quite 

 different nature. 



