VOL. LXXXIX.] PHILOSOPHICAL TRANSACTIONS. 559 



this part; and in respect to the substance which is the cause of ossification, little 

 also requires to be mentioned, for this, as before observed, is known principally to 

 consist of phosphate of lime. I shall only therefore briefly mention the results of 

 certain experiments. 



The bones of fish, such as those of the salmon, mackerel, brill, and skate, 

 afforded phosphate of lime; and the only difference was, that the bones of these 

 fish appeared in general to contain more of the cartilaginous substance, relative to 

 the phosphate of lime, than is commonly found in the bones of quadrupeds, &c. 

 The different bones also of the same fish were various in this respect; and the 

 bones about the head of the skate only differed from cartilage, by containing a 

 moderate proportion of phosphate of lime. It is at present believed that phos- 

 phate, with some sulphate of lime, constitutes the whole of the ossifying sub- 

 stance; and perhaps the formation of bone from cartilage depends only on the 

 phosphate of lime; but whether this is the case or not, it is fit that I should notice 

 a 3d substance, which constantly occurred in the course of my experiments. 



When human bones, or teeth, as well as those of quadrupeds and fish, whether 

 recent or calcined, were exposed to the action of acids, an effervescence, though 

 at times but feeble, was produced. This circumstance at first I did not particularly 

 notice, but the following experiments excited my attention. After the phosphate 

 of lime had been precipitated from the solutions of various teeth and bones, by 

 pure ammonia, I observed that a 2d precipitate, much smaller in quantity, was 

 obtained by the addition of carbonate of ammonia. This 2d precipitate dissolved 

 in acids, with much effervescence, during which carbonic acid was disengaged; 

 and selenite was formed by adding sulphuric acid. The solution of this precipitate 

 did not contain any phosphoric acid; nor did the liquor from which the precipitate 

 had been separated afford any trace of it. This precipitate was therefore carbonate 

 of lime; but I still was not certain that it existed, as such, in the teeth and bones. 



Though regular and comparative analyses of the bones of different animals have 

 not hitherto been made, yet, by the experiments of Messrs. Gahn, Scheele, 

 Macquer, Fourcroy, Berniard, and the Marquis de Bullion, it has been proved, 

 that phosphate of lime is the principal ossifying substance of bones in general, and 

 that this is accompanied by a small proportion of some saline substances, and by 

 sulphate of lime. I was therefore desirous to ascertain, whether the carbonate of 

 lime, which I had obtained by the above-mentioned experiments, had been pro- 

 duced from the sulphate of lime decomposed by the alkaline precipitant, or whe- 

 ther the greater part had not existed in the bones, in the state of carbonate. 



Each of the solutions in nitric acid afforded a precipitate with nitrate of barytes; 

 but the quantity of sulphuric acid thus separated, appeared by far too small to be 

 capable of saturating the whole of the carbonate of lime obtained from an equal quantity 

 of the solution. To prove therefore the presence of the carbonic acid, and the 

 consequent formation of carbonate of lime, portions of the various teeth and 

 bones were immersed, at separate times, in muriatic acid; and the gas produced 



