M. D'^Arcet on the Bwies of Butcher'' s Meat. 293 



only be employed upon those which do not contain any fat, or 

 upon old and dirty bones. 



The preservation of bones as an alimentary substance is of 

 the highest importance, as they easily turn to putrefaction. 



A portion of the gelatine changes into ammonia, and this, 

 by combining with the gelatine not decomposed, takes away 

 its property of turning into jelly by cold, and makes it soluble 

 in cold water. 



Various methods of preservation have been tried. In all 

 cases we should begin by depriving the bones of the fat, or 

 else they acquire in time a rancid smell, which renders them 

 useless. 



The broken bones boiled in a copper with water furnish a 

 great deal of fat, but they still retain enough to turn rancid. 

 It has been proposed to remove it by saponifying, with soda, 

 the remaining fat ; but the success has not been complete : 

 the gelatine is often altered, and retains a disagreeable smell 

 of soap. The salting, which can be applied even to the fresh 

 bones, is preferable ; if on a great scale it is not too expen- 

 sive ; and if the products are as agreeable as in the fresh 

 state. 



The method which appears to me to succeed best is that of 

 Plowden for the preservation of meat, which consists in im- 

 mersing the meat into a strgng solution of the juice of meat 

 or of gelatine, and then drying them in the open air. I took 

 a solution of gelatine containing about twenty centieraes of 

 dry gelatine ; I heated it to 80° or 90°, and I dipped in it 

 several times the clear bones, broken into little bits, and strip- 

 ped of their fat. The bones when taken out of the solution 

 of gelatine are put to dry upon strings in the open air, 

 and then treated once or twice in the same manner, to increase 

 the thickness of the layer of gelatine. It is followed by a per- 

 fect desiccation in a stove at 20° or 25°. 



The extraction of the gelatine of bones is yet but imper- 

 fectly known, and demands particular attention. It appears 

 that the first attempt was made by Papin, who proposed in 

 1681, for this end to employ condensed steam ; but the gela- 

 tine obtained by this process was almost always altered, had a 

 disagreeable empyreumatic smell, and was no longer a jelly. 



