78 IMBEDDING METHODS. 



years in the cedar oil, so that this has become thick, I remove it 

 partially or entirely by soaking in xylol (thirty minutes to several 

 hours) before putting into the paraffin. But with fresh oil of cedar 

 I find no advantage in doing so. 



GIESBRECHT'S method (Zool Anz., 1881, p. 484), is as follows : 

 Objects to be imbedded are saturated with chloroform, and the 

 chloroform and objects are gradually warmed up to the melting-point 

 of the paraffin employed, and during the warming small pieces of 

 paraffin are by degrees added to the chloroform. So soon as it is seen 

 that no more bubbles are given off from the objects, the addition 

 of paraffin may cease, for that is a sign that the paraffin has entirely 

 displaced the chloroform in the objects. This displacement having 

 been a gradual one, the risk of shrinkage of the tissues is reduced to 

 a minimum. 



MAYER (Grundziige, LEE and MAYER, 1910, p. 84) first saturates 

 the objects with benzol,, and then adds to the benzol some small 

 pieces of paraffin, and lets them dissolve in the cold. After several 

 hours (up to eighteen) the whole is brought in an open vessel on to 

 the cold water-bath, the bath is then warmed gradually so as to 

 attain a temperature of 60 C. in about two hours, and as fast as 

 the benzol evaporates melted paraffin is added to it. Lastly, the 

 paraffin is changed once before the definitive imbedding. He 

 rarely leaves objects overnight in the water-bath. 



APATHY (Mikrotechnik, pp. 149, 150) first clears with oil of cedar, 

 then brings the objects (by the process described 119) into a 

 solution of paraffin in chloroform saturated at the temperature of the 

 laboratory. The objects remain in the chloroform-paraffin solution 

 for from one to three hours, without warming, until all the cedar oil 

 is soaked out of them. The whole is then warmed on the water- 

 bath or oven to a few degrees above the melting-point of the paraffin 

 intended to be used for imbedding, and the object is brought into a 

 mixture of equal parts of paraffin and chloroform, being suspended 

 therein near the top on a bridge made of hardened filter paper (or in 

 a special apparatus to the same end, not yet described). It remains 

 in this mixture, at the temperature of the oven, for one to three 

 hours, and lastly is brought (still on the paper bridge or in the 

 apparatus) into pure paraffin, where it remains for half an hour to 

 two hours. 



DENNE (in litt., 1907) points out that the objects ought at first to 

 be at the bottom of the mixture. For this mixture is not a true 

 solution, and the lower section of the contents of the tube is com- 

 paratively free from paraffin while the upper part is nearly pure 



