Example 13 



Preparation of a Transverse Section of the Tongue of a Rat, 

 Using Celestin 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 im- 

 perfectly fixed or handled with undesirable reagents in any stage of the pro- 

 ceedings. Therefore, it is recommended that the following description 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. 



Though opinions vary widely as to the most desirable fixative to employ for 

 muscularized tissues, it may be said at once that no alcoholic solution or so- 

 lution 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 provide an excellent premordanting for the 

 staining techniques which 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 successfijlly, it must be washed over- 

 night in running water and then dehydrated. The process of dehydrating, 

 clearing, and embedding is the point at which most muscularized tissues be- 

 come unmanageable. Nothing, of course, can counteract the effect of improper 

 fixation, but even with good fixation the utmost attention must be paid to the 

 selection of dehydrating agent, clearing agent, and to the temperature at which 

 the embedding takes place. It has been the experience of the author that the 

 newer substitutes for alcohol in dehydrating tend to harden or render brittle 

 muscular tissue to a greater extent than does the more old-fashioned method 

 of using ethyl alcohol. There is little choice in the matter of clearing prior to 

 embedding, for it has been found by numerous workers that benzene has less 

 hardening effect on muscular tissue than has any other agent. 



Unless very thin sections are to be cut, it is recommended that a wax of no 



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