A NEW COMPOUND MICROTOME. By GeO. C. HuBBARD. 



Wishing to prepare some slides exhibiting the structure of various ani- 

 mal tissues and organs, but having no microtome, I made one of wood 

 chiefly, at a cost of thirty cents and two or three days' labor. 



The principle of the machine is to prepare sections by quickly forcing the 

 tissue, supported on a carrier attached to the circumference of a 12-inch 

 wheel, across the edge of a razor, which is brought automatically a slight 

 distance nearer the tissue at each rotation of the wheel. 



The base of the machine is a heavy board about thirteen inches long by 

 eight in width. At the middle of each side inflexible standards are erected 

 and adjustable bearings provided, the centre of the opening in each being 

 six and one half inches above the board. In these bearings rests the axis 

 of the 12-inch wheel, which is turned by means of a crank. 



The support for the tissue consists of a round brass disc of any conve- 

 nient size attached at its centre to one end of a short cylindrical rod. This 

 rod fits into a corresponding orifice extending through the middle of a half- 

 cleft sphere, which fits loosely in a corresponding socket in the circumfer- 

 ence of the wheel. One side (the one opposite to the automatic feeder) of 

 this socket is made adjustable by removing a round bit of wood and in- 

 serting in its stead a concave disc, which is attached to the short end of a 

 straight lever extending down the side of the wheel to near the axis. A 

 screw passing loosely through the lever about an inch from the center of 

 the disc into the wheel serves as a fulcrum. Let this lever be called A. 

 The long arm of A is moved by means of a circular wedge turning upon 

 the round end of the wheel's axis. The thick part of the wedge is allowed 

 to project four or five inches beyond the line of the circumference of the 

 circle, and provided with a knob, thus forming a second lever, B, to which 

 the power is applied. Instead of B and the wedge, a thumb-screw may be 

 screwed through the long end of A, its end turning against the side of the 

 wheel. 



When the tissue has been fastened to the brass disc in the usual way, its 

 round support is thrust into the opening of the ball. The carrier is turned 

 and bent in any direction and pushed out or in until tne tissue is in the 

 right position with regard to the razor. A slight force exerted on the knob 

 of B moves B forward thus causing a thicker part of the circular wedge to 

 pass between the wheel and the long arm of A, which forces the concave 

 disc at the other arm against the half-cleft ball, thus causing it to grip firm- 

 ly the tissue support. If a thumb-screw be used, it must be turned three 

 or four times to produce the same eflect. 



