THE necessity for providing some instrument which offered the advantages of modern microtomes and yet was within the reach of those whose work being of intermittent cliaracter did not warrant their employing the somewhat elaborate instruments that are found in laboratories, made me originate the instrument shown in figs. 83 and 84. The microtome is intended to be held in the hand during use, and is of two forms-one for ice and salt, the other for ether. The former ( fig. 83) consists of a

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... rical vulcanite chamber closed at the bottom by a brass screw-lid, and at the top by a Fro. 83. disk of vulcanite, having in the centre a plate of brass (freezing plate) 7/8 in. in diameter, and terminating in the chamber by a rod of brass. A metal cap surmounted by a glass plate and pierced in the centre to allow the freezing plate to project, screws over the upper end of the cylinder, the outer surface of which bears a male screw of hard metal on which the cap turns. As the cap is turned round a spring catch clicks at given intervals ; these are so arranged that as the cap rotates from left to right each click shows that it has sunk on to the cylinder l j l 0 0 0 in. ; hence any tissue fixed on the freezing plate projects, at each click, 1/1000 in. through the hole in the glass plato of the cap, and a 2 x 2