192 



THE MICROSCOPE AND ITS REVELATIONS. 



upon the imbedding plug. This plug may be either a cylinder of carrot, 

 turnip, potatoe, or elder-pith, cut to fit the well of the Microtome, and 

 excavated to receive the substance to be cut; or it may be a cast of the 

 interior, made either by pouring into it paraffine or some similar sub- 

 stance liquefied by heat ( 189), or by filling it with thick gum-mucilage 

 which is then rendered dense by cold ( 191). The latter plan was first 

 devised by Prof. Rutherford, whose Freezing Microtome, in which the 

 upper part of the cylinder is surrounded by a well filled with a freezing- 

 mixture, has now come into general use. The substitution of ether-spray 

 for ice-congelation was suggested by Mr. Bevan Lewis; and an improved 

 model, which can be used either as a Freezing or as an Imbedding 

 Microtome, has been devised by Messrs. Beck. An ingenious method of 

 so attaching the cutting-blade by a ' parallel motion,' as to make its edge 

 at the same time move tangentially and transversely to the plane of 

 section, has been devised by Prof. Seiler, of Philadelphia, and has found 

 much approval, as well in this country as in the United States. 1 



Rivet-Leiser Microtome; A, as seen from the front; B, as seen from behind. 



188. Rivet- Leiser Microtome. For the cutting of very thin sections 

 of soft Animal or Vegetable substances which may be advantageously 

 imbedded in paraffine or some other hard fat ( 189), no instrument is 

 more effective than that represented in Fig. 135, which is known as the 

 6 Leipzig ' or ' Rivet-Leiser ' Microtome. This has for its base an oblong 

 solid metal plate, from which rises a vertical plate, of which the upper 

 edge is inclined at a gentle angle. From either side of this vertical 

 plate, there projects a smoothly-planed plate, like a shelf sloping 

 inwards; but while the edge of one of these shelves is parallel to the base, 

 that of the other is parallel to the inclined margin of tho vertical plate. 

 On the former si ides a carrier bearing a Knife, the position of which can be 

 adjusted and fixed by means of a binding-screw that works through a slot 



1 " Journ. of Roy. Microsc. Soc.," Vol. ii. (1879), p. 329. 



