Microtome Knives These are the sharpest, most dangerous instruments for cutting and slicing in the world! (Forget about scalpels!) If wielded as a sword it would slice the victim in half without effort! Microtome – from the Greek mikros, meaning small or little; temnein, meaning to cut A microtome is an apparatus for slicing tissues into very thin slices, often cutting cells into several thin slices for study. The common blade is of highly sharpened steel, as seen in the photo. This is used to section prepared specimens embedded in paraffin, or for slicing frozen tissues in a cryotome (freeze microtome). These slices are studied using light microscopy. The sharp edge of the knife can be seen as a thin grey bevel in the photo. Then there are glass knives made by breaking squares of special hard glass into triangles, or diamond knives. These are used for ultra thin slices of plastic embedded tissues for high power electron microscopy. Section thickness can be 50 nanometers (50 X 10-5 meters or 50 X 1 billionth of a meter) to 100 micrometers (100 X 10-6 or 1 millionth of a meter). This allows for extremely thin sections that the electron beam in an electron microscope can readily show the contents of. Even large molecules can be examined in place! I have worked with all 3 types. One day, while working with a cryotome, I noticed some odd brownish spots on the floor of the instrument casing. Then another one. That’s when I discovered my little finger had come in contact with the blade edge. If my finger nail hadn’t stopped the movement, I would have lost the tip of my right pinkie! No pain until over an hour later! Healing was slow since the cut was so clean the cells and nerves did not react to the injury. But when the pain started, it was phenomenal! Vengeance of the nerves for not getting the proper signals for an injury! It took over 3 weeks to heal the cut! After that, I was even MORE careful when working with the cryotome. Part of the problem was working in the cold which reduced feeling and finger movements (COLD fingers)! So, now you’re experts on microtomes, or at least know what they are! ENJOY!