BONE. /I 



into a weak aqueous solution of i in 600 ; in a couple of 

 days it is transferred to a fresh solution of i in 400, and 

 again in a couple of days to another solution of i in 

 200. A stronger solution than this should not be used, 

 but this should be renewed every few days, and the bottle 

 frequently shaken. In two or three weeks the process 

 will probably be completed ; this can be ascertained by 

 passing a fine needle into the preparation. If it be de- 

 sirable to hasten the process, after a week or ten days' 

 soaking in chromic acid, as directed, a little nitric acid 

 may be added to the solution (i c.c. to 100 c.c.). The 

 previous action of the chromic acid will prevent the 

 swelling and partial destruction of the soft parts, 

 which nitric acid alone causes. If picric acid be 

 employed, a saturated aqueous solution should be used, 

 the preparation frequently shaken, and additional crys- 

 tals of the acid occasionally added. 



When the bone has become sufficiently soft by either 

 of these methods, it is allowed to soak for a day in 

 water to remove the excess of acid, and then hardened 

 and preserved in alcohol. Longitudinal and transverse 

 sections should be made, and, if decalcified by chromic 

 acid, are best stained double with haematoxylin and 

 eosin ; if by picric acid, the structure shows very well 

 after staining with picro-carmine. Both may be 

 mounted in glycerin. If the periosteum has not been 

 removed, its structure and relation to the bone are well 

 shown. 



Sections of Hard Bone. In such preparations as the 

 above, which are mounted in fluids, the canaliculi are 

 for the most part invisible, because the fluids which fill 



