AND HOW TO USE IT. 235 



fluid, iodised serum, or dilute albumen — any of these may be 

 used — and filter. 



4. — Salt Solution.— Dissolve 7*5 grammes sodic chloride 

 (common salt) in 1,000 cc. of distilled water. This is by far the 

 most convenient fluid to employ. Its composition is so near that 

 of lymph — the fluid normally bathing the tissues — that it alters 

 fresh tissues very slightly. 



Decalcifying Solutions. 



A good solution for softening bone may be made by mixing 

 chromic acid, i gramme ; strong nitric acid, 2 cc. : water, 200 cc. 

 When the bone is softened sufficiently to allow a fine needle to be 

 passed through it, it should be removed from the solution and 

 thoroughly washed in water, after which it must be hardened in 

 alcohol. The nitric acid removes the lime salts, whilst the 

 chromic acid hardens the parts. If the fluid is not changed, a 

 few drops of nitric acid may be added from time to time, if the 

 softening process is delayed too long. 



Hydrochloric Acid.— One part of strong acid, with 10 parts of 

 water, does well for injected bone. 



Picric Acid.— A saturated watery solution should be used ; it 

 is of great value for decalcifying fcetal bones. The mixture 

 should be frequently changed, or a few crystals added from time 

 to time. 



A 10 per cent. Solution of Common Salt and Hydrochloric 



Acid.— This is most valuable for showing the matrix of bone, which 

 consists of ordinary fibrous tissue, and swells up in the ordinary acid 

 media. A 10 per cent, solution of salt prevents this (V. Ebner and 

 De B. Birch). The bone is placed in a 10 per cent, solution of 

 common salt, to which i to 3 per cent, of hydrochloric acid is 

 added. Add from day to day as much acid as will decalcify the bone; 

 when the bone becomes flexible, it is placed for several hours in 

 water, to remove all the acid. Leave it for several days in the 10 

 per cent, salt solution, which must be changed repeatedly. When 

 the reaction of the bone becomes neutral, the bone is white and 

 opaque. Sections arc made and mounted in a 10 per cent, solu- 



