To prepare the Material for Freezing. 19 



Only one microtome will, however, be described in 

 this work, as it is very simple and does the work well. 

 This is Williams' microtome, made by Swift of Univer- 

 sity Street. It consists of a tub to contain the freezing 

 mixture, with a brass standard into which screw the 

 brass circular plates on which the material is frozen. 

 A top with a glass surface fits on to this, having a hole 

 through which the circular plate projects. The knife 

 is fixed into a triangular frame, having screws at each 

 angle by which it is raised and lowered. 



To prepare the microtome for use : 



1. Have the knife as sharp as possible. 



2. Pound some ice finely in a cloth. 



3. Scrape some salt into a fine powder. 



With a spoon, put a layer of ice into the tub and then 

 some salt on it, mix with the spoon, and so on, until the 

 tub is about half full, then ram it hard with a stick and fill 

 again, put in the salt and ice in about equal proportions, 

 leave room for the top, wipe off the salt and ice from 

 the edge, put on the top and fix it with the screw for 

 that purpose. Screw the circular plate into its place, 

 and the microtome is ready for use. 



An India-rubber tube must be fixed to carry away 

 the drainings as the ice melts. 



To PREPAKE THE MATERIAL FOR FREEZING. 



Any tissue which has been preserved in spirit, 

 must be soaked in water for 24 hours to remove the 

 spirit, and then placed in mucilage for another 24 



hours. 



c2 



