PARAFFIN METHOD 81 



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 {Grundzuge, 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 7nelted paraffin is added to it. Lastly, 

 the paraffin is changed once before the definite imbedding. He 

 rarely leaves objects overnight in the water-bath. 



Apathy [Mikrotechnik, pp. 149, 150) first clears ivith oil of cedar, 

 then brings the objects (by the process described, § 134) 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 7iear 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 Hit., 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 comparatively free from paraffin while the upper part is nearly 

 pure paraffin. He moves the holder up in the tube at intervals, 

 and the infiltration proceeds gradually with the minimum risk 

 of shrinkage. Lastly, he removes the objects, on the holder, to 

 the top of a tube of pure paraffin. 



The practice of giving successive baths first of soft and then of 

 hard paraJFm, which has been frequently advised, appears to us 

 entirely illusory. 



It is important to keep the paraffin dry — that is, protected from 

 vapour of water during the bath. 



