Artschwager described a cooling apparatus for handling paraffin ribbons during hot weather. Use of this device in our laboratory during the summer has proven highly satisfactory and at the same time it suggested to us the idea of using the same principle for keeping the knife blade cool while cutting. Accordingly, a copper box was made 12x6x4 inches, as shown in the accompanying figure. A suitable lid should be made from the same material. On the back of this box was soldered a narrow strip of copper, which was allowed to project approximately seven inches beyond the end of the box. This projecting strip should be just wide enough to fit into the groove on the back of the blade holder of the microtome, which happens to be just one-half inch in the case of the blade holder used in our laboratory. It should be soldered to the back of the box just high enough from the bottom to permit it to slide easily into the blade holder groove when the holder is in place on the microtome. This height is just three and nine-sixteenths inches for our Spencer Rotary microtome.