TOOLS AND METHODS OF WORK 25 



■^elly-like mass; each addition of celloidine must be thoroughly 

 dissolved before the next is added, stir or shake occasionally to 

 facilitate the process. 



4. Transfer the specimens from the mass with fine-pointed forceps 

 and drop them one by one into chloroform. There must be 

 sufficient celloidine adhering to the specimens to form 'a protective 

 coat. The action of the chloroform is to coagtdate or solidify the 

 celloidine and form a solid block. At first the specimens will 

 Hoat on the surface of the chloroform, but as they become 

 solidified they will sink to the bottom of the vessel ; the process 

 will be complete in six to eight hours, when any surplus celloidine 

 adhering to the specimens may be removed, and the specimens 

 placed in 92 per cent, alcohol, where they may remain indefinitely. 



In actual practice I find it preferable to use two parts of ether and 

 one part of absolute alcohol, rather than equal parts of each, — the 

 specimen works out more solid and is better to cut, celloidine also has a 

 less tendency to take up the stains. The specimens are imbedded in 

 the well of the microtome with melted paraffin, in exactly the same way 

 as the uncelloidinised specimens ; the sections are placed direct into 

 92 per cent, alcohol, from which they may be stained, then cleared with 

 oil of bergam,ot, and transferred to a thin sohition of balsam and 

 benzol, out of which they may be mounted when convenient. 



The reason for the use of oil of bergamot, in clearing 

 celloidinised sections, is that it has no appreciable action on the 

 celloidine, whereas oil of cajeput and oil of cloves dissolve the celloidine, 

 and by their use the sections would be destroyed. 



To Infiltrate Specimens with Pai'affin. 



Specimens of either vegetable or animal tissue which cannot be cut 

 sufficiently thin by the celloidinising method and by means of the 



