CHAPTEE V. 

 DOUBLE STAINING. 



BY double staining is meant a process in which two 

 colours are taken, which have affinities for different 

 elements in the tissues to which they are applied. 

 Thus while one colour will stain the connective tissue 

 and protoplasm of cells, the other will colour all nuclei 

 and so differentiate the different elements as to make 

 them more easily discernible. Others again will stain 

 different glands according to their secretions. Thus 

 showing a distinct chemical reaction between glands 

 differing in their functions. 



In other cases the duct of a gland can be stained of a 

 different colour to the surrounding tissue and its own 

 secreting substance, by which means it is easy to distin- 

 guish it, and thus show if it is implicated in any mor- 

 bid change, and also in some cases prove whether the 

 morbid change is primary in it or has extended from 

 surrounding tissues, in which case all the ducts would 

 not probably be similarly affected. 



Double staining is a subject that requires to be very 

 much more worked out than it has been hitherto, and 

 in the present work, those processes only will be given 

 in detail, which have been fairly well tried ; many other 

 combinations of staining agents will be apparent to the 

 student, which have not yet been worked out, for 

 want of time, and there is no pursuit in which patience 



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