l8 MICROSCOPICAL DIAGNOSIS. 



the ether or rigoline spray or by a mixture of ice and salt, it is frozen 

 hard enough to cut. 



When the material has been reduced to a fit condition for cut- 

 ting by the action of alcohol or- like reagents, it may be held in the 

 left hand and thin sections cut with a razor held in the right hand. 

 The razor or knife should be plane on one side and concave on the 

 other, and when cutting, the concavity should be kept flooded with 

 alcohol. Some experience is necessary in order to cut good off- 

 hand sections, and if it be desirable that the sections compare well 

 with each other in thinness, it will be necessary to employ a microtome 

 as an aid, for without this aid a large number of the sections will be 

 more or less imperfect. Before the specimen is placed in the well 

 of the microtome it should be dipped in a solution of gum arabic, 

 which is allowed to become nearly dry. Thus protected, the tissue 

 is placed in the well close to that edge which will be nearest the 

 knife when cutting and in such a position that the sections may be 

 cut in the desired direction. The warm embedding mixture is 

 poured over and around the tissue until the well is filled. The 

 microtome is now removed to a cool place when the mixture soon 

 hardens. The following are recommended as embedding mixtures: 



Solid paraffin, 3 parts. } 

 Cocoa butter, i part, v SOFT. 

 Hog's lard, 3 parts. ) 



Solid paraffin, 2 parts. 



Cocoa butter, i part. HARDER. 



Spermaceti, i part. 



Solid paraffin, 3 parts. } 

 Cocoa butter, 2 parts. V HARD. 

 Spermaceti, i part. ) 



Paraffin, 2 parts. } TRANSPARENT 



AND 

 Vaseline, i part. ) EASY TO CUT. 



STAINING. 



After the sections have been cut it will be necessary to stain 

 them in order to differentiate their several parts. The following are 

 a few formulae in general use: 



