VOL. LXXXIX.] PHILOSOPHICAL TRANSACTIONS. 523 



phosphoric acid, when the substance is in too small a quantity to be examined in 

 any other manner. Similar experiments, on the substance of teeth formed on 

 pulps, and on common bone, afforded similar results. 



Mr. Hatchett considers lime and phosphoric acid to be the essentially constituent 

 principles of these 3 different structures ; and any difference that is met with, only 

 seems to be that which would constitute species of the same genus, similar to what 

 is found in the mineral kingdom, under lime-stone, marble, and calcareous spar; 

 these differ only by a small change in the proportions of their constituent principles, 

 and by a different arrangement of their integrant particles. The head of a human 

 thigh bone was found, some years since, with a thin crust of highly-polished enamel, 

 similar in some respects to that of the teeth, on a portion of its surface, an inch 

 and half in length, and an inch in breadth; the cartilage having been previously 

 removed by disease. This uncommon appearance, at the time, could not be ac- 

 counted for; but the fore-mentioned observations, on the formation of the enamel 

 of the teeth, appeared to throw some light on it; and Mr. H., at my request, made 

 the following experiment, to determine whether the synovia, in a healthy state, 

 contains phosphate of lime. 



960 gr. of synovia, by a gradual evaporation, afforded 21 gr. of a substance which 

 resembled dried glue. This being collected was put into a small porcelain crucible, 

 which, placed in a larger crucible, was exposed to a red heat, during nearly an hour. 

 The matter in the porcelain crucible was much reduced in bulk, and appeared like 

 a glazing, thinly spread on those parts of the crucible which had been in contact 

 with it in its former state. Boiling distilled water was digested on the matter in the 

 crucible, for some time. This water afterwards afforded, with acetite of lead, a 

 copious precipitate of phosphate of lead; but no appearance of lime could be ob- 

 tained. On the residuum in the crucible, acetous acid was digested, which was 

 afterwards divided into 2 portions. To one of these, solution of acetite of lead was 

 added, and as before afforded a plentiful precipitation of phosphate of lead. To the 

 other portion was added oxalic acid, by which a small quantity of a precipitate was 

 obtained, which was an oxalate of lime. Phosphate of lime is therefore present in 

 synovia, though but in a small quantity; and as, from these experiments, there is 

 reason to believe, that more phosphoric acid was obtained than was requisite to 

 saturate the lime, it seems probable, that part of it was combined, in the synovia, 

 either with soda or ammonia; and this accounts for the part dissolved by the dis- 

 tilled water. 



M. Margueron, in the Annales de Chimie, (vol. 14, p. 123,) estimates the pro- 

 portion of water in 288 gr. of the synovia of an ox at 232 gr. The other ingre- 

 dients therefore amount to 56 gr.: but by evaporation Mr. Hatchett obtained, from 

 960 gr. of synovia, only 21 gr. of residuum; which proves that the proportion of 

 water is much greater; for 56 to 288 is as 1 to 5.14; but 21 to 960 is as 1 to 45.7 J. 

 It is possible, that the proportion of water to the other ingredients may not always 

 be the same. M. Margueron also probably estimated the albuminous matter, &c. 



3 x2 



