MICROSCOPIC TECHNIQUE. 17 



drum. As soon as the object is removed from absolute alcohol it 

 should be thoroughly dried with blotting paper. If it is desired to 

 embed with paraffin, the specimen should be placed in xylol, chloro- 

 form, turpentine, or cedar oil for at least twelve hours, and then 

 transferred to a solution of paraffin and xylol, allowing it to remain 

 twelve to twenty-four hours. It may now be transferred to melted 

 paraffin, which should be kept as little above the melting point as 

 possible. After remaining until it becomes thoroughly saturated 

 with the paraffin, which usually requires from twelve to twenty- 

 four hours, it may then be embedded. To infiltrate with celloidin, 

 two solutions are necessary, a thin and a thick. The celloidin is dis- 

 solved in equal parts of absolute alcohol and ether. To make the 

 thin solution, use five grams of celloidin in 100 cc. of the mixture. 

 The second solution should have the consistency of thick sirup. The 

 dehydrated tissue is placed in a mixture of equal parts of absolute 

 alcoHol and ether from twelve to forty-eight hours, then in the thin 

 solution for about the same period. It may remain in the thick 

 solution twenty-four hours, or longer if desired. It is then ready for 

 embedding. 



4. Embedding in paraffin Embedding L's or paper boxes may be 

 used. To accomplish this process, the following method may be 

 pursued: Place upon a pane of glass a clean piece of paper. Ar- 

 range the embedding L's so as to form a receptacle of the required 

 size. Pour into this a small quantity of melted paraffin. Now ar- 

 range the tissue in the position desired and fill the receptacle with 

 paraffin. As soon as the paraffin becomes sufficiently hardened the 

 embedding L's may be set in a vessel containing ice-cold water. Care 

 should be taken that the water does not run over the top of the 

 paraffin. 



To Embed with Celloidin. A cork or block of wood which has 

 been soaked in equal parts of absolute alcohol and ether may be 

 used. Place upon the cork or block a small quantity of thick cel- 

 loidin.. Then place in position the piece of tissue and cover it with 

 the celloidin, adding a little at a time, layer after layer as each 

 hardens, until the tissue is completely embedded. The whole may 

 now be transferred to chloroform for one or two hours, and then 

 to seventy-five per cent alcohol, where it may be left indefinitely. 

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