ANATOMICAL TECHNIQUE 453 



firmly pressed for a moment on the prepared surface of one of the 

 wood-blocked cylinders. After resting for ten or fifteen minutes 

 in a warm place it becomes securely fixed and is ready for cutting. 

 The knives for cutting hard vegetable materials should not be 

 too thinly ground on the edges. The type of edge supplied by 

 the Jung firm under the designation of c answers very well for the 

 purpose. The knives are best not too large in size and should not 

 exceed eight inches in length. They are sharpened by the aid of a 

 cylindrical appliance slipped over the back, which gives the edge 

 a less acute angle to the sharpening stone, with a corresponding 

 advantage in saving of time. The stone or hone for putting the 

 edge of the knife in condition should be preferably a yellow Belgian 

 one, such as is ordinarily employed by barbers, but of considerably 

 larger size and of as fine texture as can be procured. It is better, 

 in fact, to have two stones, one coarser for preliminary use and a 

 finer one for finishing. Carborundum hones, although often sup- 

 plied for the purpose of sharpening microtome knives, are not 

 advantageous. In renewing the edge of the knife care should at 

 first be taken to remove all hacks or gaps by grinding on a coarse 

 hone. In the sharpening process the edge of the knife should be 

 pushed forward on the stone and not backward, as the latter pro- 

 cedure results in a so-called "wire edge." After the removal of 

 the nicks the edge is finished on a finer hone. If, as a result of 

 frequent sharpening, the knife has been ground away to a very 

 thick edge and consequently sharpens very slowly, it is necessary 

 to grind it on an alundum or carborundum wheel of very fine tex- 

 ture. The knife is held on a support known as a knife-grinder and 

 brought against the revolving wheel at such an angle that the edge 

 is slightly hollow-ground. It requires a little skill to grind a knife 

 on the wheel, but this is quickly acquired and the frequent sending 

 of the knives to the cutler is thus avoided. A further advantage of 

 grinding the knives in the laboratory is the avoidance of drawing 

 of the temper, which is often the unfortunate result of sending 

 them to a professional grinder. The wheel should be revolved at 

 a high rate of speed and the edge of the knife held gently against 

 it. In this manner overheating is avoided. The grinding machines 

 furnished by the Carborundum Company of Niagara Falls and the 



