562 PHILOSOPHICAL TRANSACTIONS. [ANNO 1709. 



according to their vicinity with such membranes or cartilages as are liable to such 

 a change. If horns are examined, few I believe will be found to contain phos- 

 phate of lime in such a proportion as to be considered an essential ingredient. I 

 would not be understood to speak here of such as stag or buck horn, for that has 

 every chemical character of bone, with some excess of cartilage; but I allude to 

 those in which the substance of the horn is distinctly separate from the bone, and 

 which, like a sheath, covers a bony protuberance which issues from the os frontis 

 of certain animals.* 



Horns of this nature, such as those of the ox, the ram, and the chamois, also 

 tortoise shell, afford, after distillation and incineration, so very small a residuum, 

 of which only a small part is phosphate of lime, that this latter can scarcely be re- 

 garded as a necessary ingredient. By some experiments made on 500 gr. of the 

 horn of the ox, I obtained, after a long continued heat, only 1.50 gr. of residuum; 

 and of this, less than half proved to be phosphate of lime. 78 gr. of the horn of 

 the chamois afforded only 0.50 of residuum ; and 500 gr. of tortoise shell yielded 

 not more than 0.25 of a gr., of which, less than half was phosphate of lime. 

 Now it must be evident, that so very small a quantity cannot influence the nature 

 of the substances which afforded it ; and the same may be said of synovia, 480 gr. 

 of which did not yield more than 1 gr. of phosphate of lime. This substance is 

 undoubtedly various in its proportions, in all these and other animal substances, 

 arising probably from the age and habit of the animal which has produced them ; 

 but I believe that I may, at least, venture to place some confidence in the fore- 

 going experiments, as several others, made since the above was written, have tended 

 to confirm them. -J- 



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

 the fossil bones of Gibraltar, as well as some glossopetrae or shark's teeth. The 

 latter afforded phosphate and carbonate of lime ; but the carbonate of lime was 

 visibly owing principally to the matter of the calcareous strata which had inclosed 

 these teeth, and which had insinuated itself into the cavities left by the decomposi- 

 tion of the original cartilaginous substance. The bones of the Gibraltar rock also 

 consist principally of phosphate of lime; and the cavities have been partly filled by 

 the carbonate of lime which cements them together. Fossil bones resemble bones 

 which, by combustion, have been deprived of their cartilaginous part; for they 

 retain the figure of the original bone, without being bone in reality, as one of the 



* Nature seems here to have made an analysis or separation of horn from bone. — Orig. 

 ■f These experiments were repeated on bladder, which I chose in preference to any other membrane, 

 as not being liable to ossification, and therefore likely to contain very little or no phosphate of lime. 

 250 gr. of dry hogs' bladder, after incineration, left a residuum the weight of which did not exceed 

 J^j of a gr. This was dissolved in diluted nitric acid ; and, on adding pure ammonia, some faint traces 

 of phosphate of lime were observed. Now as 250 gr. of bladder did not afford more than -^ of a gr. 

 of residuum, of which only a part consisted of phosphate of lime, there is much reason to regard thig 

 experiment as an additional proof, that phosphate of lime is not an essential ingredient of membrane. — 

 Orig. 



