1892.] THE MICROSCOPE. 159 



WAVS • 



AND MEANS- 



Imbedding Delicate Objects in Celloidin. — The object, 

 properly fixed and hardened, is placed for twenty-four hours in a 

 mixture of equal parts of alcohol and ether. It is then transferred 

 to a thin syrujDy solution of celloidin, made by dissolving celloidin 

 in a mixture of equal parts of alcohol and ether. After remain- 

 ing in this solution for about twenty-four hours the object is cov- 

 ered with a thicker solution of celloidin, and is allowed to remain 

 in the same for about twenty-four hours, when it is ready to im- 

 bed on cork. 



When ready to imbed the object, a small quantity of the celloi- 

 din solution is spread on clean glass (a slide will answer the pur- 

 pose) , and allowed to dry. Then another coat is applied, and 

 allowed to dry. This affords a firm celloidin bed upon which 

 the object is placed and arranged, care being taken to place it in 

 the desired position as quickly as possible before the celloidin 

 begins to harden. The whole is now covered with successive 

 layers of the celloidin solution until a firm support is built up for 

 the object. When sufficiently dry, the celloidin is removed from 

 the glass by means of a sharp knife, and if necessary a pair of 

 scissors is used to trim the bed to the proper size and form. It 

 is now ready to imbed on cork. 



The top of a cork is coated with celloidin solution and allowed 

 to dry. This is done to prevent air from rising from the cork and 

 forming bubbles in the celloidin. The object, in its matrix of 

 hardened celloidin, is placed in the desired position on the cork, 

 and fastened to it with celloidin. After drying in the air until a 

 layer is formed on the outer surface firm enough to retain the 

 shape, the cork is dropped into 50 -per cent, alcohol. Usually the 

 object is ready to cut after remaining one hour. 



This method of preparing a bed of celloidin has been employed 

 with very satisfactory results in obtaining sections of embryo 

 chicks. Blastoderms of the earlier periods of incubation have 

 been successfully sectioned. By arranging the embryo on the 

 bed of hardened celloidin it has been possible to get large sym- 

 metrical sections of the blastoderm. Celloidin contracts during 

 the drying process, but, by the exercise of due care in arranging 

 the blastoderm, distortion may be avoided. 



This method of imbedding has given good results in studying 

 hydra, and the preparation of the celloidin bed may be resorted 

 to in almost every case where delicate objects are to be sectioned. 



