CALDWELL S AUTOMATIC MICROTOME. 649 



crucible answers very well; if care is taken not to allow it to 

 become hotter than is sufficient to thoroughly melt it. Take a 

 piece of glass and smear it with a very small quantity of 

 glycerine^ to prevent the embedding material from sticking to 

 it. Then pour the melted material on the glass, in small 

 quantities at a time, so as to get a layer nearly a quarter of an 

 inch thick. This when cut up into suitable pieces with a 

 knife does very well for embedding small objects. If larger 

 objects are required it is well to have two pieces of brass of 

 the form shown in fig. 5, which, when placed together, will 

 form a cavity half an inch in depth, and of any desired length 

 up to an inch or more ; this cavity may be filled with the 

 melted material in the manner as already described, and the 

 object to be cut must then be placed in position while the 

 material is fluid. It is well to cool the material as rapidly as 

 possible by placing it in water as soon as it is sufficiently set. 

 From the cake thus formed, or from the piece cast in the 

 mould, cut the piece of the material containing the object, and 

 with an old scalpel, heated in a Bunsen flame, melt a small 

 hole in the paraffin containing the cylindrical vessel (fig. 1, a), 

 and insert the piece of embedding material containing the 

 embedded object; then with the heated scalpel melt a little of 

 the paraffin round the base of the projecting piece, so as to 

 give it firm support, and allow this to become thoroughly set. 



Now remove the large brass plate from the top of the micro- 

 tome (fig. 1, b), and insert the vessel containing the embedded 

 object in the tube for its receptioa, having first oiled the tube 

 slightly to prevent the vessel from sticking. Next with a 

 sharp knife cut the material with the object embedded in it, so 

 that all its opposite sides are parallel. This is extremely impor- 

 tant. Replace the top plate and fix the razor in the holder 

 provided for the purpose. The clamp is so made that if a 

 little care is taken the edge of the razor will not be injured 

 (fig. 6). The razor must be set so that its back is as high as 

 possible, as shown in fig. 6, and above all the razor must be 

 extremely sharp. It should be sharpened on a stone and not 

 on a strop. The sharpness of the razor and the accurate 



