260 On Cutting Sections of Animal Tissues 



numberless scratches, giving it a confused appearance; but this 

 may be easily removed by polishing the section on a glass plate, 

 with a little Tripoli or fine emery powder ; a piece of leather firmly 

 spread on a flat piece of wood, with a little powder sifted over it, 

 will also answer the same purpose. 



2nd Method. — The bone is sawn into lamellae, as in the first 

 method, or by a thin circular rotating saw, then ground down to a 

 moderate thinness on a small grindstone, made to rotate in an ordi- 

 nary lathe, the stone being kept moistened with water. It should 

 then be further ground on both sides on a fine flat whetstone, also 

 rotating, and finally polished as in the previous instance. The 

 sections obtained by both processes should be cleaned in water, 

 either with a camel's-hair brush, or — which is far preferable — a soft 

 toothbrush, and dried ; they are then ready to be put up in Canada 

 balsam or dry. The last method was adopted and used by the late 

 Mr. Carter for many years. A sufficient guarantee of its success 

 is the splendid collection of sections of bones and teeth, made by 

 him, in the possession of the Royal Microscopical Society. 



Bones may be prepared either by removing the surrounding 

 tissues with a scalpel, and drying, or, after cleaning in this manner, 

 steeping them for some months in a large quantity of water, which 

 should be changed occasionally to prevent putrefaction. During 

 the maceration they should be scrubbed from time to time with a 

 hard brush ; and when perfectly clean, they should receive a final 

 scrubbing in clean water, and dried by exposure to the atmosphere, 

 By simply drying, a bone, saturated with fat, is generally the 

 result, from which a dry, white specimen cannot readily be ob- 

 tained ; by the latter process, however, a perfectly white bone — 

 — especially if it be from a dropsical subject — will be the reward 

 for time and patience expended on it. 



II. Tissues of Intermediate Density. — Under this head may 

 be classed decalcified bone, cartilage, tendon, and many tissues 

 hardened by chromic acid, and other agents. 



Sections of bone prepared by the methods already described, 

 although very instructive and beautiful, do not show the soft 

 organic structure, but only the bony framework ; if we desire to 

 exhibit the relations existing between the periosteum, blood-vessels, 

 and nerves, it will be necessary to soften the bone ; to effect this, 

 after being cleaned from surrounding tissue, it is to be placed in a 

 large quantity of one of the following solutions: — Chromic acid, 

 3 or 4 per cent. ; or a mixture recommended by Professor Ruther- 

 ford,* consisting of nitric acid, 2 per cent. ; chromic acid, 1 per 

 cent. When the softening is carried on in this solution, the tissues 

 assume a bright green colour, due to the decomposition or reduction 

 of the chromic acid into sesquioxide of chromium, Cr 2 ;j . Nitric 



* Rutherforrl, No. 45, ' Quarterly Journal of Microscopical Scieuce.' 



