on Shell and Bone. 29 



Moreover, as the prefence of phofphate of lime, mingled with 

 carbonate, appears to be a chemical charafter of crultaceous 

 marine animals, there is every reafon to conclude that Lin- 

 naeus did right not to place the echini among the teftaceous 

 ones. 



The prefence of phofphate of lime in the fubftance which 

 covers the cruftaceous marine animals appears to denote an 

 approximation to the nature of bone, which, not only by the 

 experiments of Mr. Gahn, but by the united teftimony of all 

 chemifts, has been proved principally to conliil: (as far as the 

 oilifying fubilance is concerned) of phofphate of lime. 



This confideration, therefore, induced me to repeat the 

 above experiments on the bones of various animals. 



It is fcarcely neccflary for me to mention the ufual cfFecls 

 of acids on bones fteeped in them, as they are known to every 

 phyfiologift and anatomift. 



In every operation of this nature the ofiifying fubftance, 

 which is principally phofphate of lime, is difTolved, and a 

 cartilage or membrane of the figure of the original bone re- 

 mains; fo tha^ the firft origin of bones appears to be by the 

 formation of a membrane or cartilage of the requifite figure, 

 which, when the fubfequent fecretion of the ofiifying fub- 

 ftance takes place, is penetrated by, and thus becomes more 

 or lefs converted into the fl:ate of bone. 



It is alfo known that the nature of the bone is more influ- 

 enced by the greater or lefs predominance of the membrana- 

 ceous or cartilaginous part than by any other caufe. It is 

 not, therefore, for mc to add any thing to this part : and in 

 rtfpect to the fubftance which is the caufe of offification, little 

 alfo requires to be mentioned ; for this (as has been already 

 obferved) is known principally to confift of phofphate of 

 lime. I fhall only, therefore, briefly mention the refult of 

 certain experiments. 



[To be continued,] 



VII. Flijlorj 



