4 6 



PRACTICAL HISTOLOGY. 



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ether. The first, or weaker solution, is made of a thin consistence 

 like collodion duplex, the other is made stronger, until it has a thick 

 syrupy consistence. 



The hardened tissue is placed for some time in absolute alcohol, 

 and then for several days, or until it is completely saturated, in a 

 mixture of equal parts of "absolute alcohol and ether. After this it 

 is placed in a glass-stoppered bottle in the thin solution of celloidin 

 until it is completely saturated with it (23 days). Transfer the 

 tissue to syrupy celloidin, and let it remain there for several days 

 until the tissue is thoroughly infiltrated with celloidin. 



Some use three strengths of celloidin solution : 



(1.) A thick syrup consistence. 



(2.) One part of (1) diluted with 2 vols. of ether. 



(3. ) One part of (2) diluted with 2 vols. of ether. 



After thorough infiltration the tissue has to be embedded. For 

 this purpose make a paper box (fig. 30) ; or use a pill-box, or embed 

 it on a cork, thus. Take a cork corresponding 

 to the size of the object, roughen one end of 

 it, and surround it with a piece of paper 

 fastened by a pin (fig. 31). Moisten the 

 roughened surface with absolute alcohol, and 

 on it place the tissue infiltrated with celloidin, 

 and surround the latter with the thick solution 

 of celloidin. Allow it to stand until the cel- 



Uloidin begins to harden on the surface. This 

 takes place in less than an hour. Place the 

 box or cork, as the case may be, in 80 per cent, 

 alcohol for 24-48 hours, which hardens the 

 celloidin to such a consistence that it can be 

 cut like a stiff cheese, but the sections must be 

 cut with a knife wetted with 70 per cent. 

 alcohol. It is immaterial which microtome is 

 used, as long as the knife is moistened with 

 not too strong alcohol. The sections may be transferred to alcohol 

 or water, and stained with any suitable dye. Some dyes stain the 

 celloidin, especially the aniline dyes, and others do riot. 



A section after being stained may be mounted in glycerine or 

 balsam, but in the latter case absolute alcohol cannot be used to 

 dehydrate them, as celloidin is soluble in this fluid. Alcohol (95 

 per cent.) must therefora be used for this purpose. Moreover, the 

 sections must be clarified by origanum or bergamot oil not by oil 

 of cloves, which has a solvent action on the celloidin and mounted 

 in balsam. (See also Clarifying Reagents.) 



Objects embedded in celloidin may be kept ready for cutting for 

 an indefinite time in 75-80 per cent, alcohol. 



FIG. 31. Embedding 

 Paper Box with 

 Weight for Cel- 

 loidin with a lead 

 " Sinker." 



