33^ Journal of*Compakative Neurology. 



For the actual imbedding, a mixture of hard and soft 

 paraffin is chosen, which, at the temperature of the room, 

 will cut without too great a tendency to roll. If too hard, 

 the paraffin rolls into a close scroll, which not only is difficult 

 to smooth upon the slide, but tends to fracture and distort 

 the tissue. It is well to experiment on a block of the paraffin 

 in which the tissue is to be imbedded beforehand. 



For summer, a fusing point of about 30° C. is desirable. 

 In lieu of a thermo-regulator, when the latter is unavailable, 

 a copper plate supported on a tripod will serve to conduct 

 the heat from the gas flame at one end to a narrow metal 

 tray at such a distance as may be necessary to keep the 

 paraffin just fvised. The brain is suspended in the tray in 

 any convenient way to avoid contact with the metal. Even 

 the tinned spoons frequently used may conduct too much heat 

 heat to the object. A beaker over a water bath is a simpler 

 but less reliable method. 



Care must be exercised in removing the brain from alco- 

 hol to turpentine, and in all subsequent removals, to avoid 

 contact with (especially moist) air. The alcohol must be 

 absolute, and should be used in sufficient quantity. 



The imbedding is performed in the usvial way. An 

 oblong box is made by folding writing-paper, and a layer of 

 the paraffin is allowed to cool on the bottom, say one-eighth 

 of an inch think. When this has solidified a small portion 

 of paraffin is heated nearly to boiling in a spoon and poured 

 into the tray, so as to partly fuse the surface of the solidified 

 layer. This precaution prevents the flaking oft' of the first- 

 formed layer. The box is then filled with paraffin from the 

 tray containing the specimen, which is orientated carefully 

 on the paraffin bottom, and pinned out if necessay. Gener- 

 ally the viscid layer will serve to hold the specimen in any 

 desired position. When cooled, if the work has been care- 

 fully done, the whole mass solidifies about the specimen. 



In cutting longitudinal horizontal sections the brain 

 should be orientated to begin cutting from the dorson, in 



