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The first thing to be done is to choose a material corre- 

 sponding in firmness Avith the object about to be cut. By- 

 melting together common solid paraffin (the paraffin candles 

 sold at the shops answer very well) with the so-called paraffin 

 oil, a substance may be obtained with almost any melting 

 point you like, and setting, on being cooled, into almost any 

 degree of firmness you please. A mixture of about one 

 quarter or less of paraffin oil to three fourths of paraffin 

 candle has appeared to me most generally useful. 



Supposing the object to have been hardened in chromic 

 acid, and to be about to be mounted in balsam, the way to 

 proceed is as follows. 



The object is taken out of the chromic acid and immersed 

 for a few hours in alcohol. A cake of the paraffin mixture 

 is then cut of a size suitable for holding in the hand ; a hole 

 scooped in it, and a small quantity of the melted parafliu 

 poured in. The object, previously taken out of the alcohol, 

 and its wetness removed, either with blotting paper, or by 

 evaporation, is then dropped in. If the paraffin be suf- 

 ficiently liquid the object will sink a little way in it, and the 

 under surface will soon become com])letely coated with the 

 paraffin. So much paraffin only should be used as is enough 

 to cover the lower half of the object, the upper portion re- 

 maining uncovered. The exact position of the object must 

 now be noted, in order that there may be afterwards no 

 doubt of the plane in which the section is to be made. An 

 arrow marked on the cake, or, if necessary, a sketch in ink, 

 will prevent all difficulties. As soon as by the cooling of 

 the paraffin the object has become fixed, more paraffin is 

 poured over it until it is thoroughly covered in. The cake 

 with the imbedded object is now thrown into spirit, and in a 

 few minutes is ready for section, though it is, on the whole, 

 better to let it stay in the spirit till the next day. 



The cake must afterwards be carefully pared away, a little 

 at a time, in the plane of intended section, until the object 

 is seen to shine through. The sections may then be made 

 either with a microtome or with a hand razor. If the cut 

 surface be kept well Avetted with spirit, and a layer of spirit 

 be carefully carried on the upper surface of the razor, 

 there will be no difficulty in floating the section on to a 

 glass slide ; the movement may be aided by a pipette or 

 syringe. It is often useful to bevel down the edges of the 

 cake, from time to time, as sections continue to be made, in 

 order that as little paraffin as possible may be carried away 

 on the razor with the section. 



If the specimen be not intended for mounting in bal- 



