292 CORROSION, DECALCIFICATION, AND BLEACHING. 



decalcifying power, but cause great swelling. Picric acid 

 has a very slow action, and is only suitable for very small 

 structures. 



560. Nitric Acid (Buscn, 1. c.). To all other agents Busch 

 prefers nitric acid, which causes no swelling and acts most 

 efficaciously, whilst at the same time it does not injuriously 

 attack tissue- elements. 



One volume of chemically pure nitric acid of sp. gr. 1'25 is 

 diluted with 10 vols. water. It may be used of this strength 

 for very large and tough bones ; for young bones it may be 

 diluted down to 1 per cent. 



Fresh bones are first laid for three days in 95 per cent, 

 alcohol; they are then placed in the nitric acid, which is 

 changed daily, for eight or ten days. They must be removed 

 as soon as the decalcification is complete, or else they will 

 become stained yellow. When removed they are washed for 

 one or two hours in running water and placed in 95 per cent, 

 alcohol. This is changed after a few days for fresh alcohol. 



Young and foetal bones may be placed in the first instance 

 in a mixture containing 1 per cent, bichromate of potash and 

 y 1 ^ per cent, chromic acid, and decalcified with nitric acid of 

 1 to 2 per cent., to which may be added a small quantity of 

 chromic acid (-^ per cent.) or chromate of potash (1 per cent.). 

 By putting them afterwards into alcohol the well-known 

 green stain is obtained. 



Staining agents. Sections of bone treated in the last- 

 described manner are stained five or ten minutes in a weak 

 aqueous solution of eosin. The ground-substance and small 

 cells of cartilage remain colourless, the nuclei of the large 

 cells are stained red, and so is periosteum, bone-tissue, and 

 the cellular contents of the medullary spaces. Hsematoxylin 

 may be used in conjunction with eosin (before or after it) to 

 obtain double-stains, which, however, are seldom successful. 



Sections are dehydrated in absolute alcohol, and mounted 

 (without clearing by oil of cloves or the like) in a benzol- 

 solution of Canada balsam. 



561. Nitric Acid and Alcohol. 3 per cent, of nitric acid in 

 70 per cent, alcohol. Soak specimens for several days or 

 weeks. I do not know who first recommended this admirable 

 medium. 



