298 CHEMICAL TRANSFORMATIONS. 



cause ; a fact which shows^ that their molecules have 

 assumed another position, and that they possess, 

 therefore, a certain degree of mobility, even in the 

 condition of a solid. A very rapid transposition or 

 transformation of this kind is seen in arragonite, a 

 mineral which possesses exactly the same compo- 

 sition as calcareous spar, but of which the hardness 

 and crystalline form prove that its molecules are 

 arranged in a different manner. When a crystal of 

 arragonite is heated, an interior motion of its mole- 

 cules is caused by the expansion ; the permanence 

 of their arrangement is destroyed ; and the crystal 

 splinters with much violence, and falls into a heap 

 of small crystals of calcareous spar. 



It is impossible for us to be deceived regarding the 

 causes of these changes. They are owing to a dis- 

 turbance of the state of the equilibrium, in con- 

 sequence of which the particles of the body put in 

 motion obey other affinities or their own natural 

 attractions. 



But if it is true, as we have just shown it to be, 

 that mechanical motion is sufficient to cause a change 

 of condition in many bodies, it cannot be doubted 

 that a body in the act of combination or decompo- 

 sition is capable of imparting the same condition of 

 motion or activity in which its atoms are to certain 

 other bodies : or in other words, to enable other 

 bodies with which it is in contact to enter into com- 

 binations, or suffer decompositions. 



The reality of this influence has been already suffi- 

 ciently proved by the facts derived from inorganic 

 chemistry, but it is of much more frequent occurrence 

 in the relations of organic matter, and causes very 

 striking and wonderful phenomena. 



By the tevms fermentation^ putrefaction, and erema- 

 causiSy are meant those changes in form and prop- 

 erties which compound organic substances undergo 

 when separated from the organism, and exposed to 

 the influence of water and a certain temperature. 

 Fermentation and putrefaction are examples of that 



