66 MOUNTING AND PREPARATION OF OBJECTS. 



that in which an attempt has been made to use ether 

 as the freezing agent. 



The microtome is attached to a firm table, the 

 piston well oiled and the brass table polished ; near 

 at hand, we place the razor and a strop, as it requires 

 sharpening after two or three sections have been cut. 



A block of ice splintered by a sharp awl, is pounded 

 as fine as possible and placed in an earthen-ware 

 crock or other suitable receptacle. An equal quan- 

 tity of coarse salt being put in a similar vessel. 



The razor and a clean camel's hair brush are placed 

 in a dish containing water to which a small quantity 

 of alcohol has been added. 



The cylinder is nearly filled with thick gum. One 

 of the pieces of tissue or organ being submerged in 

 it, the orifice is covered by an inverted watch glass, 

 and the box filled with alternate spoonfuls of ice and 

 salt. The mixture must be tightly rammed round 

 the cylinder, care being taken not to stop up the 

 drainage tube. 



The freezing should proceed slowly, and only be 

 carried far enough to cause the gum and tissue to 

 assume a grizzly consistency. If they become white 

 and icy looking it has been carried too far, and time 

 must be allowed for their return to a proper condi- 

 tion before using the razor. 



The rough top being sliced off and the razor well 

 wetted with spirit and water, the handle is grasped 

 by the right hand the edge being turned from us. 



A slight turn is now given to the screw to elevate 

 the cylinder of gum above the level of the table, 



