M. Von Buch on the Silicificatiwi of' Organic Bodies. 57 



logical form, but it is actually calcareous spar, and hence is no 

 more an organic substance. The secretion of the calcareous spar, 

 and its being kept as a surrounding substance, may be indispen- 

 sably necessary for the life of the animal ; just as the secretion 

 of apatite (phosphate of Imie), and its being amassed in the 

 form of bones, may be necessary to the existence of animals hav- 

 ing an osseous skeleton. Thus, it is as little entitled to be con- 

 sidered an organic substance, or such as appertains to the ojiera- 

 tions of life, as the serpentine, marble, or fragments of shells would 

 be, with which the Trochus agglutinans builds or strengthens his 

 dwelling; or as the shell in which the Pagurus Bernardus con- 

 ceals itself, and without which it could not live. The substance 

 of shells, as well as of bones, obey entirely mineralogical laws. 

 And when the apatite (phosphate of lime) cannot be recognis- 

 €h1 in the form of a bv)ne, it will still have lost as little of its na- 

 ture, as the calcareous spar, when the hand of the sculptor has 

 converted it into a marble statue. Life, pursuing its work en- 

 closed in an independent circle, seeks, in the steadiness and ri- 

 gidity of mineral substances, for protection from the principle of 

 gravity, which destroys all animated beings. 



The skeleton of animals would have become very different, 

 had nature had another substance to work with than phosphate 

 of lime, the axes of which are unequal. I have been told that, 

 in the foetus, the formation of the skull begins from a central 

 point, from which it extends around in the form of rays. 



Such minerals only as have unequal axes, i. e. in which there 

 is one axis of greatest contraction, can become fibrous, or extend 

 themselves in rays. They are those minerals in which the axis 

 of the ray is always at the same time, the axis of the greatest 

 contraction. This axis ever decides the predominant direction 

 of the shooting out of the rays. It is only in such minerals 

 that these rays can so arrange themj^elves together, as to form a 

 thin covering. 



Were the secreted substance one having equal axes, like fluor- 

 spar, for instance, the organic life would have had thus great 

 difficulty in arranging the particles of fluor-spar when formed. 

 Instead of rays and plates, masses would have l)een produc- 

 ed ; and the skeleton, and with it the entire animal and its ca- 

 pabilities, would have been completely different from what they 

 actually are. 



