42 PRACTICAL HISTOLOGY. 



medium is made to penetrate into the tissue, and when it sets, it thus 

 supports all its component parts. This method is extremely valuable, 

 especially for brittle and friable tissues, and is largely used. More- 

 over, the tissues once embedded can be kept in a box, each duly 

 labelled, for any length of time. 



Make a mixture of two parts of hard paraffin and one part of 

 soft ; place the mixture in a small copper pan or capsule in a hot- 

 air oven, kept at a constant temperature by means of a gas regu- 

 lator. The gas supply must be so arranged that the thermometer 



FIG. 29. Mayer's Paraffin Embedding Bath, as made by Jung of Heidelberg. 



steadily registers at most i C. above the melting-point of the 

 paraffin. Or the paraffin may be melted and kept melted in a 

 little copper vessel, placed in a hot- water bath, kept at a constant 

 temperature, as shown in fig. 29. The temperature is kept con- 

 stant by means of a gas regulator, R Z is for filling the instru- 

 ment with water ; a, 7>, c, are embedding vessels and pots. 



The tissues to be saturated and embedded should not be large, 

 and they must be thoroughly dehydrated ; keep them, therefore, 

 several hours in absolute alcohol. Place them direct into tur- 

 pentine, creosote, benzol, toluol, or xylol- some use chloroform, bu'3 



