SECTIONS OF SOFTENED BONE. 103 



large proportionate amount of the fluid must be 

 used. For example if the bone be a long bone 

 about the size of the human metacarpal, a piece not 

 longer than a quarter of an inch should be sawn 

 from it and placed (suspended by a thread if pos- 

 sible) in a beaker capable of containing some 200 

 c. c. of the chromic acid solution. If the bone be 

 larger, it is well to split the disk thus sawn off into 

 three or four smaller pieces, since otherwise the 

 decalcification will occupy too long a time. The 

 acid used should be at first very weak (1 in 600) ; 

 in two days' time this may be changed for a solu- 

 tion of 1 in 400 ; and this again in another two days 

 for 1 in 200. Beyond this the strength of the acid 

 should not be increased, but the fluid should be 

 renewed every three days at least. In addition to 

 this frequent changing of the liquid, it should, 

 throughout the whole time of softening, be stirred 

 as often as possible: this is of the greatest impor- 

 tance, for every agitation brings fresh portions of 

 acid to attack the earthy matter of the bone. By 

 attention to this particular the time which the 

 pieces take to become thoroughly decalcified may 

 be materially shortened. The completion of the' 

 process is ascertained by passing a needle through 

 the middle of the piece employed ; if it meets with 

 no gritty obstruction, all the earthy matter is pro- 

 bably got rid of. This will most likely be the case 

 in two or three weeks from the commencement of 

 the operation. Should the pieces of bone, owing to 

 their too great thickness or density, be much longer 

 than this" before they are sufficiently soft, the pro-. 

 cess may be hastened by adding to the chromic acid 

 solution a little nitric acid (2 c. c. to each 100 c. c. 

 of chromic solution). This reagent was not avail- 

 able at the commencement of the operation, because, 

 although it would have more readily dissolved the 

 salts of lime than the chromic acid, yet it would 

 have softened still more the included soft tissues of 

 the bone instead of hardening; them like that re- 



