APPENDIX II 679 
oblique angle to the frame and drawn across the block with a 
long sliding motion. The knife and the top of the celloidin 
block must be constantly kept wet with 80 per cent. alcohol. 
The feed mechanism is covered to protect the 
Fic. 507.—Rotary microtome. 
a (Courtesy Spencer Lens Co.) 
wearing parts from dust. 
The object is placed in the object carrier and clamped in. 
By means of the graduated disk at the base of the feed mecha- 
nism the thickness, in terms of microns, is regulated after each 
stroke of the razor. 
