134 American Quarterly Microscopical /ourtial. 



knife made with a stiff handle, expressly for cutting thin sec- 

 tions, should be used in connection with the microtome, and 

 should be kept as sharp as frequent stropping can make it. 



It will be found that the edge of the knife has a bevel, pro- 

 duced by honing and stropping, which will raise the cutting- 

 edge above the glass plate when the flat side of the knife is 

 laid on the plate, and will cause the knife to cut upward and 

 out of the tissue, thus breaking the section before it is com- 

 pleted ; or, if the operator is conscious of this upward tendency 

 and endeavors to correct it, alternate bands of thick and thin 

 portions will be observed in the section. This difficulty can be 

 obviated by raising the back of the knife slightly, so as to cause 

 it to slide on the bevel. It will also be found, that it is much 

 easier to cut a large thin section with a knife, the edge of which 

 is perfectly straight, than with one that has a curved edge, as is 

 always the case with razors. This is because the slightest 

 variation in the inclination of the knife toward the glass plate 

 or ring, will cause the curved edge to gouge into the tissue as 

 it passes through it, and the result will be either a wedge- 

 shaped or a wavy section. It will be^ seen, therefore, that the 

 knife should be carried through the tissue with an even motion 

 and at the same inclination to insure success. This is, however, 

 not as easy as might be imagined, because the hands usually 

 are not sufficiently steady without a great deal of practice 



It occurred to me some time ago that if the knife could be 

 rigidly fastened to some apparatus, by means of which it could 

 be moved over the well of the microtome in the same manner 

 that the hands move it, sections of any size and thinness could 

 easily be made, even by an unpractised hand. After some ex- 

 perimenting I constructed, with the valuable aid of my friend, 

 Mr. Joseph Zentmayer, a mechanical microtome, which, on 

 working with the finished model made for me by Mr. Zent- 

 mayer, proved to be all that can be desired in an apparatus of 

 this kind. 



It consists of two rigid, parallel arms of metal, which atone 

 end revolve on pivots attached either to the microtome itself, 

 or to the table to which the microtome is to be clamped. On 

 the other end of these arms are fastened revolving clamps 

 which hold the knife, the edge of which, when in position, 

 rests upon the glass plate of the microtome. The handle of 

 the knife is removed, so as to prevent a slipping and a hinder- 



