DISTINCTIVE CHARACTERS OF ORGANIZED BODIES. 17 



CHAPTER I. 



OF THE VITAL OPERATIONS OF ANIMALS, AND THE INSTRUMENTS BY 

 WHICH THEY ARE PERFORMED. 



1. LIVING beings, whether belonging to the Animal or to 

 the Vegetable kingdom, are distinguished from the masses of 

 inert matter of which the Mineral kingdom is made up, by 

 peculiarities of form and size, of structure, of elementary 

 composition, and of actions. Wherever a definite form is 

 exhibited by Mineral substances, it is bounded by plane 

 surfaces, straight lines, and angles, and is the effect of the 

 process of crystallization, in which particles of like nature 

 arrange themselves on a determinate plan, so as to produce a 

 regular aggregation; and there is, probably, no Inorganic 

 element or combination which is not capable of assuming such 

 a form, if placed in circumstances adapted to the manifestation 

 of its tendency to do so. The number of different crystalline 

 forms is by no means large ;' and as many substances crystal- 

 lize in several dissimilar forms, whilst crystals resembling one 

 another in form often have a great diversity of composition, 

 there is no constant correspondence between the crystalline 

 forms and the. essential nature of the greater number of 

 mineral substances. If that peculiar arrangement of the 

 molecules which constitutes crystallization should be wanting, 

 so that simple cohesive attraction is exercised in bringing 

 them together, without any general control over their direc- 

 tion, an indefinite or shapeless figure is the result. "With 

 this indefiniteness of form, there is an absence of any limit 

 whatever in regard to size : a crystal may go on increasing 

 continuously, so long as there is new material supplied ; but 

 this new material is deposited upon its surface merely, and 

 its addition involves no interstitial change ; the older particles, 

 which were first deposited, and which continue to form the 

 nucleus of the crystal, remaining just as they were. In Or- 

 ganized bodies, on the other hand, we meet with convex 

 surfaces and rounded outlines, and with a general absence of 

 angularity ; and the simplest grades, both of Animal and of 



