the leaf. The mycelium of a mould developed in a solution of Bismarck brown was clearly stained after having been washed in water, whilst it is known that the mycelium, which frequently forms in coloured solutions, picro-carmine, hæmatoxylin, &c., remained perfectly colourless. Other aniline colours injected under the skin of frogs stained the connective tissue as deeply as did the Bismarck brown; but the striæ of muscle remained colourless. We may conclude, then, that Bismarck brown possesses the quality of colouring living protoplasm both in plants and in animals. Cutting, Grinding, and Mounting Hard Structures. Take the femur of cat, or rabbit, remove as much of the muscle as possible and macerate it in water until quite clean; on removal hang it up to dry. With a fine saw make transverse and longitudinal sections. File the section down until flat, and smooth. Take some Canada balsam, place a piece on a square of glass and warm gently over a lamp until the balsam is plastic enough to allow of the section being pressed into it, and set it aside to consolidate. Take a hone (“Water-of-Ayr” stone), moisten it with water, and rub one side of the section upon it until quite smooth, then place the glass slip, with the section still attached, into methylated spirit, and in a very short time the section will be separated; wash it and remount it on the reverse side, and proceed to rub it down on the hone until it appears to be thin enough for mounting. Polish both sides on a polishing strop with Tripoli powder, and mount in Canada balsam. [Illustration: Fig. 244.--Small Lathe for cutting and polishing Sections of Teeth.]