INTRODUCTION. \*J 



It is more convenient, if the specimen is stained 

 in toto previous to the imbedding. If this procedure 

 is not adopted, it is necessary to remove the imbed- 

 ding mass from the sections in order to stain them. 

 This may be accomplished by placing them in tur- 

 pentine, which dissolves out the paraffin, then re- 

 placing the turpentine with alcohol. 



Celloidin and Paraffin. This double 'method of 

 imbedding is extremely useful for specimens com- 

 posed of tissues of different densities, /.<?., the finger- 

 nail and nail-bed. The specimen is first impregnated 

 with celloidin in the usual manner and then immersed 

 in chloroform to coagulate the celloidin. The fur- 

 ther manipulation is the same as described above 

 for imbedding in paraffin. 



MOUNTING. 



Sections, bits of dissociated tissue, membranes, 

 etc., having been duly prepared, they are to be 

 mounted on a slide for study. The choice of a fluid 

 for this purpose will depend upon the nature of the 

 specimen, the mode of preparation to which it has 

 been subjected, and the structural features which 

 we wish especially to demonstrate. One of .the 

 fluids most frequently employed for this purpose is 

 glycerin. Many of the hardening agents, such as 

 alcohol, precipitate, as above remarked, certain 

 albuminoid substances in the tissues, in the form of 

 minute strongly refractive particles, thus rendering 



