THE METHODS OF MOUNTING MICROBES 87 



tome is smeared on its upper surface with a solution 

 of celloidin, which is left to harden. When the 

 material is ready, it is mounted upon a prepared 

 cork (i.e. it is placed on the smeared surface) ; and 

 a little celloidin solution is poured over the material 

 so as to cover it. The mounted material is now 

 placed in 70 per cent, alcohol in order to harden 

 the celloidin (which has a pasty consistence). In a 

 few hours or so the imbedded material will be 

 ready for cutting with one of the microtomes already 

 described. Schanze's microtome is a useful instru- 

 ment for cutting sections of materials imbedded in 

 celloidin. In cutting a tissue imbedded in celloidin 

 or mounted directly on cork, the razor and tissue 

 should be kept wet with alcohol, and the sections 

 carefully transferred to alcohol. The sections (if 

 from celloidin material) are placed in oil of cloves 

 in order to dissolve out the infiltrated celloidin. 

 They are then ready for staining, etc. 



For fixing pieces vifirm materials directly on corks 

 either glycerine-gelatine l or gelatine is used. These 

 substances are liquefied by the application of heat. 



Paraffin wax for use as an imbedding material is 

 first dissolved in chloroform, and then used in a 

 similar manner to the solution of celloidin already 

 described. The imbedded material must be cut 

 perfectly dry, and the sections removed to xylol. 



1 Glycerine-gelatine is prepared as follows : to 10 parts of 

 gelatine add sufficient water to allow the gelatine to swell up ; 

 pour off the water, and melt the gelatine. To the melted gela- 

 tine add 10 parts of glycerine, and finally a few drops of some 

 germicidal agent, preferably carbolic acid. The latter is added 

 in order to preserve the glycerine-gelatine. 



