MENTAL CONSTITUTION OF ANIMALS. 257 



a little mass which, decomposed, is but so much common 

 dust ; yet in its living constitution, designed, formed, and sus- 

 tained by Almighty Wisdom, how admirable its character ! 

 how reflective of the unutterable depths of that power by which 

 it was so formed, and is so sustained ! 



In the mundane economy, mental action takes its place as a 

 means of providing for the independent existence and the 

 various relations of animals, each species being furnished 

 according to its special necessities and the demands of its 

 various relations. The nervous system the more comprehen- 

 sive term for the organic apparatus on which this action 

 depends is variously developed in different classes and 

 species, and also in different individuals, the volume or mass 

 bearing a general relation to the amount of power. Passing 

 over the humblest orders, where nervous apparatus is so obscure 

 as hardly to be traceable, we see it, in the nematoneura of 

 Owen, 1 in filaments and nuclei, the mere rudiments of the 

 system. In the articulata, it is advanced to a double nervous 

 cord, with ganglia, or little masses of nervous matter at fre- 

 quent intervals, and filaments branching out towards each side ; 

 the ganglia near the head being apparently those which receive 

 nerves from the organs of the senses ; and this arrangement is 

 only less symmetrical in the mollusca. Ascending to the 

 vertebrata, we find a spinal cord, with a brain at the upper 

 extremity, and numerous branching lines of nervous tissue, an 

 organization strikingly superior ; yet here, as in the general 

 structure of animals, the great principle of unity is observed. 

 The brain of the vertebrata is merely an expansion of the 

 anterior pair of the ganglia of the articulata, or these ganglia 

 may be regarded as the rudiment of a brain, the superior organ 

 thus appearing as only a further development of the inferior. 

 There are many facts which tend to prove that the action of 

 this apparatus is of a nature allied to electricity, a modifica- 

 tion of that surprising agent, which takes magnetism, heat, 

 and light, as other subordinate forms, and of whose general 

 scope in this great system of things we are only beginning to 

 have a faint conception. It has been found, for example, that 

 simple electricity, artificially produced, and sent along the 

 nerves of a dead body, excites muscular movement. Nor is 

 this a very startling idea, when we reflect that electricity is 

 almost as immaterial as ever mind was supposed to be. It is 



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1 Including rotifera, entozoa, echinodermata, &c. 



S 



