Improved Knife-Holders for Thin-sectioning with Rotary Microtomes.

A modification of the knite holder for thin-sectioning microtomes has been described. A cam and lever arrangement, timed with the cutting cycle, advances the knife edge to the cutting position on the down stroke of the instrument and withdraws the knife edge approximately one-half mm on the return stroke. This modification permits the routine cutting of serial ribbons of uniform thinness. The ribbons are flattened upon the surface of an acetone-water meniscus and can be lifted directly on to suitably coated wire grids for electron microscopy. Sections as thin as 0.025 /x have been prepared routinely.