IMBEDDING 25 



bone with a liberal supply of the above in about twenty days. A 

 frequent change of the solution will greatly facilitate the process, 

 and an occasional addition of a few drops of the nitric acid may be 

 made with very dense bone. After the 'removal of the lime salts, 

 the pieces may be preserved in alcohol until such time as sectioi 

 are needed, when they may be cut with the microtome without 

 injury to the knife. 



DISSOCIATING PROCESS (w. STIRLING) 



Artificial Gastric Fluid 



Pepsin 1 gram. 



Hydrochloric acid 1 c.c. 



Water 500 c.c. 



This process depends for its value upon the fact that certain 

 connective tissues are more rapidly dissolved by the fluid than 

 others. 



IMBEDDING 



The best and thinnest sections can only be cut when properly 

 hardened tissues are used, and when the meshes of the tissue have 

 been filled with some substance which supports the delicate elements. 

 The substances used for this purpose are paraffin and celloidin, or 

 collodion. 



THE PARAFFIN METHOD 



a. Pieces of tissue 2-3 mm. thick are to be placed in ninety- 

 five per cent, alcohol for twenty -four hours. 

 1). In pure chloroform six to eight hours. 



c. In a saturated solution of paraffin in choloroform two to 

 three hours. 



d. In melted paraffin, having a melting point of 50 C., which 

 requires the use of a water bath or oven, one to six hours. The 

 chloroform must be entirely driven off, and the tissue thoroughly 

 infiltrated. 



e. Change to fresh paraffin for a few minutes. 



/. Finally jplace the tissue in a small paper box and pour the 

 melted paraffin about it. Harden as quickly as possible with run- 

 ning water. It is important to fix the piece of tissue in a suitable 

 position, if the position is of importance, before pouring in the 

 melted paraffin. 



