Margaret
Back in the late sixties, I use to cut frozen sections on whole human hearts (cross sections for nerve studies) using a large sliding microtome with a CO2 freezing plate, and a large 220 mm knife.  They were not difficult to section, once you got the tissue to the correct temperature.  The sections were stained by free floating them in large dishes, then I mounted them on eight inch square sheets of 3/16th plexyglass, and coversliped them with unsilvered Xray film. These large microtomes were comon at that time, but where you would find one now I have no idea.  About the largest section that you could cut with our puny little modern microtomes is about one inch in width, because the forces on the blade as it move through the tissue distorts the various parts of these microtomes, causing chatter, thick and thin sections, and other problems. Freezing a 3cm piece of tissue in LN2 is difficult if you can not cut the fresh tissue to a thinness of about 2mm befor freezing.  This is not as critical with the CO2 freezing plate.  Food for thought.
Kerry Beebe
Kelowna General Hospital
B.C. Canada