186 



A New Freezing Microtome. 



capable of doing much, is not quite so perfect as the followiag 

 modification adopted by me some months ago. This new apparatus 

 answers the purpose so satisfactorily, that it is now full time for 

 me to pubHcly direct attention to it. The apparatus consists 

 (Fig. 1) of a brass plate (B) with a hole in its centre (A). This 



Fig. ]. 



Kutherford's Microtome. — A, a Hole in the brass plate (B). C, Tube. D, Screw. 

 E, Indicator. F, Screw for fixing the machine to a table. G, Box for holding a 

 freezing mixture. H, Tube for permitting the water to flow from the melting ic e; 



hole leads into the interior of a vertical tube (E) with a movable 

 bottom (K, Fig. 2), which may be raised or depressed by means 

 of a screw (D). The tissue to be frozen and cut is placed in the 

 tube (A). The section is made by means of a knife, which is glided 

 horizontally through the tissue that projects above the level of the 

 brass plate (B). The thickness of the section is regulated by an 

 indicator (E). The machine is fixed to a table by means of a 

 screw (F), and it may be employed for two objects — 1st, for cutting 

 tissues hardened in the ordinary way by chromic acid, &:c. ; and, 

 2nd, for cutting tissues hardened by freezing. The second method 

 of using the machine will be more readily comprehended after a 

 description of the first, which is simply this : Place a portion of 

 hardened tissue, say a piece of spinal cord hardened by chromic 

 acid, in the hole (A), and pour around it a mixtui'e of parafl&n (five 

 parts) and hog's lard (one part) melted by the aid of a gentle heat. 

 Or the paraffin mixture may be first poured into the hole, and the 

 piece of tissue thereafter introduced and held in any desired position 



