58 PllACTICAL HISTOLOGY. 



Williams' Freezing Microtome (fig. 42). This consists of a 

 wooden, non-conducting tub for holding the freezing mixture. 

 Vertically in the centre of this rises a brass cylinder, into whose 

 upper end the roughened brass plate on which the tissue is frozen 

 can be screwed. The lid of the box is formed by a glass plate fitted 



FIG. 43.' Swift's Ether-Freezing Microtome. 



into a framework or kind of cap for the tub. In the centre of the 

 glass plate is a circular hole into which the freezing-plate projects. 

 In this instrument the tissue remains fixed, while the knife or blade 

 is depressed by the movement of a screw. The knife or razor is fixed 

 in a brass tripod frame-work or knife-carrier. 



