362 APPENDIX. 



placed in a large quantity of chromic acid *1 p.c. It 

 is well to shake gently occasionally, in order to bring 

 fresh acid in contact with the bone. The fluid should 

 be renewed in 24 hours, and changed for '25 p.c. acid 

 in about two days. After a week a solution of 

 5 p.c. may be used. This also may with advantage 

 be changed once or twice. The decalcification of 

 fully developed bone will take about a fortnight, but 

 a preliminary section should be made from one end 

 with a blunt razor or scalpel to see that all salts are 

 extracted. 



To hasten the solution of the salts, 1 c.c. of nitric acid 

 may be added to each 100 c.c. of the chromic acid 

 solution, but this should only be used when the 

 tissue has been for 2 to 3 days in the dilute chromic 

 acid ; as soon as the salts are dissolved the tissue 

 should be transferred to alcohol. 



Instead of chromic acid, picric acid (either Kleinen- 

 berg's or a saturated aqueous solution) may be used, 

 or the tissue may be placed in strong spirit for a 

 day or two and the salts then extracted with nitric 

 acid 1 to 4 p.c. ; as soon as this is complete the tissue 

 should be replaced in spirit. A mixture of nitric 

 acid 1 to 3 p.c. and strong spirit is often useful to 

 complete the solution of salts in tissues which have 

 been hardened in chromic acid but from which the 

 salts have been only partially extracted. 



fluid. Dissolve 25 grms. of potassium bi- 

 chromate and 10 grins, of sodium sulphate in 1000 

 c.c. of water. 



Picric acid. Make a cold saturated solution of picric 



