Experiments And OhfcTvaliom on Shell and Bone, 533 



of bone, with fome excefs of cartilage ; but I allude to thoie in which the fubftance of the 

 horn is diflin£lly feparate from the bone ; and which, like a {heath, covers a bony protu- 

 berance, which iffues from the os frontis of certain animals *. 



Horns of this nature, fuch as thofe of the ox, the ram, and the chamois, ajfo tortoife- 

 Ihell, afford after diftillation and incineration, fo very fmall a refiduum, of which only a 

 fmall pajt is phofphate of lime, that this latter can fcarcely be regarded as a neceffary 

 ingredient. 



By fome experiments made on 500 grains of the horn of the ox, I obtained, after a long 

 continued heat, only 1,50 grains of refiduum ; and of this lefs than half proved to be 

 phofphate of lime. 



78 grains of the horn of the chamois afforded only 0,50 of refiduum ; and 500 grains of 

 tortoife-fliell yielded not more than 0,25 of a grain, of which lefs than half was phofphate 

 of lime. 



Now it muft be evident, that fo very fmall a quantity cannot influence the nature of the 

 fubflances which afforded it ; and the fame may be faid of fynovia, 480 grains of which 

 did not yield more than one grain of phofphate of lime. 



This fubflance is undoubtedly various in its proportions, in all thefe and other animal 

 fubftances, arifing probably from the age and habit of the animal which has produced 

 them ; but I believe that I may at leaft venture to place fome confidence in the foregoing 

 experiments, as feveral others made fince the above was written, have tended to confirm 

 them t- 



In the courfe of making the experiments which have been related, I examined the foffil 

 bones of Gibraltar, as well as fome gloffopetrae, or (bark's teeth. The latter afforded 

 phofphate and carbonate of lime ; but the carbonate of lime was vifibly owing principally 

 to the matter of the calcareous flrata which had inclofed thefe teeth, and which had infi- 

 nuated itfelf into thefe cavities, left by the decompofition of the original cartilaginous 

 fubftance. 



The bones of the Gibraltar rock alfo confifl principally of phofphate of lime ; and the 

 cavities have been partly filled by the carbonate of lime which cements them together. 



Foffil bones refemble bones, which by combuftion have been deprived of their cartilagi- 

 nous part ; for they retain the figure of the original bone, without being bone in reality, 

 as one of the mod effential parts has been taken away. Now fuch foffil, or burned bones, 



• Nature feems here to have made an analyfij, or reparation of horn frora bone. 



•J- Thefe experiments were repeated on bladders, which I chofe in preference to any other membrane, as 

 not being liable to oflification, and therefore likely to contain very little, or no phofphate of lime, i^<» 

 grains of dry hog's bladder after incineration left a refiduum, the weight of which did not exceed -j^ of a 

 grain. This was diflblved in diluted nitric acid; and upon adding pure ammoniac, fome faint traces of 

 phofphate of lime were obferved. Now as 250 grains of bladder did not afford more than -y'g of a grain of 

 refiduum, of which only a part confifted of phofphate of lime ; there is much reafon to regard this experi- 

 ment as an additional proof, that the phofphate of lime is not an cflential ingredient of membrane. 



Vol. III. — March 1800. 3Z can 



