128 FORMATION OF 8HELLS OF ANIMALS, ETC., 
there results, after their decomposition, not only the 
necessary combination of lime with carbonic acid, but a 
compound containing also the requisite animal matter, it 
may be inferred that the coalescing particles of a similar 
composition, demonstrable on ossifying membranous 
tissues, are formed precisely on the same principles, the 
membrane on which the phosphate and carbonate are 
precipitated presenting the alkaline carbonate, and the 
blood furnishing the earthy compounds. As respects the 
precise manner in which the alkali, demonstrable in the 
crustacean, is produced, there is the same difficulty in the 
vital theory as in the physical explanation, and for the 
present both are equally inexplicable. However, it is 
much more probable that the production of this alkaline 
carbonate should be the effect of electricity, than of the 
direct agency of life. Electricity is a well-known decom- 
posing power, and electrical combinations are sufficiently 
common in animal bodies. The electric power of the 
torpedo may be taken as an example, but I am not aware 
that there is any proof that life, acting by itself, ever pro- 
duced any of those phenomena which can be exhibited 
experimentally on inanimate matter. Now, im the process 
of calcification, as in that of ossification, the carbonate 
and phosphate of lime are always precipitated on a mem- 
branous tissue of some form or other, either presenting 
markings or wholly homogeneous, this depending upon 
some particular function performed by the membrane, and 
not at all connected with the formation of shell or of bone. 
For, however disimilar these membranous structures are 
in different parts of the same animal, or in different 
animals, the deposit in its primary condition is always the 
same. After the first precipitation and coalescence of the 
earthy matter, either in the form of rings, or in that of 
i eee 
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