and Observations on Shell and Bo?ie, 325 
distinguishes the crustaceous from the testaceous substances; 
and that the principal difference in the qualities of each, when, 
complete, is caused by the proportion of the hardening sub- 
stances, relative to the gluten by which they are cemented ; or 
by the abundance and consistency of the gelatinous, membra- 
naceous, or cartilaginous substance, in and on which, the car- 
bonate of lime, or the mixture of carbonate and phosphate of 
lime, has been secreted and deposited. Moreover, as the pre- 
sence of phosphate of lime, mingled with carbonate, appears to 
be a chemical character of crustaceous marine animals, there 
is every reason to conclude that Linnaeus did right not to place 
the Echini among the testaceous ones. 
The presence of phosphate of lime, in the substance which 
covers the crustaceous 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 testimony of all 
chemists, has been proved principally to consist (as far as the 
ossifying substance is concerned) of phosphate of lime. 
This consideration, therefore, induced me to repeat the above 
experiments, on the bones of various animals. 
It is scarcely necessary for me to mention the usual effects 
of acids on bones steeped in them, as they are known to every 
physiologist and anatomist. 
In every operation of this nature, the ossifying substance, which 
is principally phosphate of lime, is dissolved, and a cartilage or 
membrane, of the figure of the original bone, remains ; so that 
the first origin of bones appears to be by the formation of a 
membrane or cartilage, of the requisite figure, which, when 
the subsequent secretion of the ossifying substance takes place, 
MDCCXCIX, U U 
