EXAMPLE 15 



Preparation of a Transverse Section of the Tongue 



of a Rat, Using Celestine Blue B Followed 



by Picro Acid Fuchsin 



The chief difficulty in preparing a transverse section of the tongue is to 

 avoid the hardening of the muscle, which tends to become brittle either if 

 imperfectly fixed or handled with undesirable reagents in any stage of the 

 proceedings. Therefore, it is recommended that the following descrip- 

 tion be followed rather closely, for it can be adapted almost without 

 variation to any other heavily muscularized tissues which it is desired 

 to stain. 



The tongue may be removed most easily by severing the articulation of 

 the lower jaw and removing this together with the adherent tongue, which 

 may be detached with a short scalpel or cartilage knife. A portion of the 

 tongue, approximately 5 mm in length, is cut off and placed in a large 

 volume of the selected fixative. 



Although opinions vary widely as to the most desirable fixative to em- 

 ploy for muscularized tissues, it may be said at once that no alcoholic 

 solution or solution containing picric acid or mercuric chloride can be 

 employed under any circumstances. The author's choice would be the 

 solution of Petrunkewitsch, which he has employed most successfully on 

 a variety of heavily muscularized tissues. This formula would also pro- 

 vide an excellent premordanting for the staining techniques that follow. 

 Whatever formula is selected, however, a very large volume should be 

 employed and permitted to act for no longer than is necessary to secure 

 the complete impregnation of the tissues. If the operator does not wish 

 to employ a copper formula, it may be suggested that he use any formula 

 containing nitric acid or one of the weaker dichromate mixtures. When the 

 piece has been fixed successfully, it must be washed overnight in running 

 water and then dehydrated. The process of dehydrating, clearing, and 

 embedding is the point at which most muscularized tissues become un- 

 manageable. Nothing, of course, can counteract the effect of improper 



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