82 PRACTICAL HISTOLOGY. 



BONE. 



1 1 8. Method of preparing Unsoftened Bone. The bone 

 is cut into tolerably small pieces, and freed from its soft parts by 

 maceration for months in water changed from time to time. The 

 bone must not be allowed to become dry previous to maceration, 

 otherwise the bony tissue may become indelibly marked with greasy 

 stains. In the case of a long bone, much of the fat may be rapidly 

 detached from the medullary canal and cancellated tissue by connecting 

 it to a water-tap by an elastic tube. The bone is then dried, and if it 

 contain much spongy tissue, it is impregnated with a strong solution of 

 gum, hardened for a day in methylated spirit, dried, and then cut with 

 a fine saw in any desirable direction. The spongy tissue is supported 

 by the gum, and thus rendered less liable to be fractured by the saw. 

 The sections are ground sufficiently thin by rubbing them on an ordi- 

 nary hone, moistened with methylated spirit to retain the gum in situ. 

 They are then placed in water to remove the gum, thoroughly washed 

 in a stream of water, and finally dried. (Ranvier.) They are com- 

 monly mounted dry, that is to say, in air. They may also be mounted 

 in dammar ( 347, c) ; this is apt to render them too transparent. 



119. Method of preparing Softened Bone. The 



soft parts of bone may be successfully hardened and pre- 

 served, while the calcareous matter is removed, by macera- 

 tion in | per cent chromic acid, with the addition of i per 

 cent nitric acid, after the method described in 15. When 

 the decalcified bone is transferred to rectified spirit, it 

 becomes of a greenish tint, owing to the production of 

 chromium sesquioxide (chromic oxide). The softened 

 bone may be readily sliced with a knife, or torn into shreds 

 for the demonstration of its lamellae. 



Ranvier recommends for the softening of bone a 

 saturated solution of picric acid, and this, for fcetal bone, 

 is perhaps the best agent. The bone should be divided 

 into very small pieces and placed in a large quantity of the 

 fluid, kept saturated by the presence of an excess of the 

 crystals. When softened, the picric acid may be partially 

 or completely removed by immersion in water or spirit. It 

 should be wholly removed only when the preparations are 

 to be stained, c.g., in picro-carmine. 



120. Staining Agents for Softened Bone. a. The 

 greenish coloration of the matrix by chromic oxide has 

 been alluded to in 119. 



