6t CUTTIXG SECTIONS OF SOFT TISSUES. 



to examine tissues without delay. Dr. Lockhart Clarke made his 

 sections of brain and spinal cord in the following manner. It is 

 an interesting contrast to the freezing method just described : — 

 The tissue is cut into fragments of moderate size, which are first 

 soaked for 24 hours in a lluid composed of equal parts of alcohol 

 and water, then for 24 hours in pure alcohol. Then the pieces 

 are immersed in dilute Chromic Acid (straw coloured), or solution 

 of Potassium Bichromate in water (i to 200), for some luccks^ or 

 until they are found hard enough to be cut. The sections are 

 rendered transparent by soaking them in turpentine, if necessary. 



Now I proceed to the plan devised by Dr. Klein, or some of the 

 German Histologists, for cutting sections without apparatus. The 

 tissue must first be hardened by the method of procedure just 

 described, or by soaking in methylated spirit only, which is 

 sufficient for most animal structures ; others do better when 

 steeped in a one or two per cent, aqueous solution of Potassium 

 Bichromate. In either case several days of soaking are required 

 before the tissue can be cut ; but supposing that a fragment 

 has been rendered firm enough by one of the methods given, 

 it is to be mounted in wax as follows : — 



White wax is melted with about one-fourth of its weight of 

 olive oil in a porcelain dish, and the two are well mixed together. 

 When cool, the wax should be cut with a razor to try its 

 consistency, and if it is hard enough to cut into very thin slices 

 without breaking, it will do. Then a little paper or cardboard 

 trough is made, (about ij-inch long, \ an inch deep, and the 

 same broad,) and set on a firm and level surface, — the wax is 

 melted by holding the porcelain dish over a lamp, — and poured 

 into the trough till three-quarters full. Now thrust a fine needle 

 into the piece of tissue to be cut — which should be a cube about 

 one-sixth inch each way — and dip the tissue into the melted wax; — 

 take it out and hold it in the air to cool; — then dip again, holding 

 it up as before, and repeating the process until it is well coated ; 

 then hold it in the middle of the trough till the wax begins to set, 

 and fill up the trough with more melted wax. When the whole is 

 cool, strip off the paper mould ; and cutting away the wax until the 

 imbedded tissue appears, slice tissue and wax together with a thin 

 razor dipped in spirit. The slices are to be taken off the razor 

 while it is immersed in spirit, as, if thin enough, they are very 

 fragile. (Before describing the mounting, it will be as well to 

 say that the "Army Razor," sold by Messrs. Arnold, of Smithfield, 

 is well adapted for section cutting, as it has a very thin and wide 

 blade.) 



The sections which appear eligible having been selected, they 

 are next to be taken from the methylated spirit on a flat instru- 

 ment, and deposited in clear spirit first, and then in the staining 



