34 NATURAL BODIES. 



state of our knowledge, the catenation cannot be esteemed rigidly 

 maintained. 1 Let us inquire into the great characteristics of the dif- 

 ferent kingdoms, and endeavour to describe the chief points in which 

 living bodies differ from those that have never possessed vitality, and 

 into the distinctions between organized bodies themselves. 



1. DIFFERENCE BETWEEN INORGANIC AND ORGANIZED BODIES. 



Inorganic bodies possess the common properties of matter. Their 

 elements are fixed under ordinary circumstances. Their study con- 

 stitutes Physics, in its enlarged sense, or Natural Science. Organized 

 bodies have properties in common with inorganic, but they have like- 

 wise others superadded, which control the first in a singular manner. 

 They are beings, whose elements are undergoing constant mutation, 

 and the sciences treating of their structure and functions are Anatomy 

 and Physiology. 



They differ from each other in 



1. Origin. Inorganic bodies are not born: they do not arise from 

 a parent : they spring from the general forces of matter, the parti- 

 cles being merely in a state of aggregation, and their motions regulated 

 by certain fixed and invariable laws. The animal and the vegetable, 

 on the other hand, are products of generation ; they must spring from 

 beings similar to themselves ; and they possess the force of life, 

 which controls the ordinary forces of matter. Yet it has been sup- 

 posed, that they are capable of creating life ; in other words, that a 

 particular organization presupposes life. This is not the place for 

 entering into the question of generation. It will be sufficient at present 

 to remark, that in the upper classes of animals, the necessity of a pa- 

 rent cannot be contested ; the only difficulty that can possibly arise 

 regards the very lowest classes ; and analogy warrants the conclusion, 

 that every living being must spring from an egg or a seed. 



2. Shape. The shape of inorganic bodies is not fixed in a deter- 

 minate manner. It is true, that by proper management every mineral 

 can be reduced to a primitive nucleus, which is the same in all minerals 

 of like composition ; still, the shape of the mineral, as it presents itself 

 to us, differs. Carbonate of lime, for example, although it may always 

 be reduced to the same primitive nucleus, assumes various appearances ; 

 being sometimes rhomboidal; at others, in regular hexahedral prisms; 

 in solids, terminated by twelve scalene triangles, or in dodecahedrons, 

 whose surfaces are pentagons. In organized bodies, on the contrary, 

 the shape is constant. Each animal and vegetable has the one that 

 characterizes its species, so that no possible mistake can be indulged ; 

 and this applies not only to the whole body, but to every one of its 

 parts, numerous as they are. 



3. Size. The size of an inorganic body is by no means fixed. It 

 may be great, or small, according to the quantity present of the parti- 

 cles that have to form it. A crystal, for example, may be minute, or 

 the contrary, according to the number of saline particles in the solu- 

 tion. On the other hand, organized bodies attain a certain size, at 



1 Fleming's Philosophy of Zoology, i. 4. Edinburgh, 1822. 



