240 MENTAL CONSTITUTION OF ANIMALS. 



masses of nervous matter at frequent intervals, and filaments 

 branching out towards each side ; the ganglia near the head 

 being apparently those which send out nerves to 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 nume- 

 rous branching lines of nervous tissue,( 98 ) 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 an electric nature, a modification 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 that simple electricity, artifi- 

 cially produced, and sent along the nerves of a dead body, 

 excites muscular movement. The brain of a newly-killed 

 animal being taken out, and replaced by a substance which 

 produces electric action, the operation of digestion, which had 

 been interrupted by the death of the animal, was resumed, 

 showing that the brain, in one of its capacities or powers, is 

 identical with the galvanic battery. Nor is this a very 

 startling idea, when we reflect that electricity is almost as 

 metaphysical as ever mind was supposed to be. It is a thing 

 perfectly intangible, weightless. A mass of metal may be 

 magnetized, or heated to seven hundred of Fahrenheit, 

 without becoming the hundredth part of a grain heavier. 

 And yet electricity is a real thing, an actual existence in 

 nature, as witness the effects of heat and light in vegetation 

 the power of the galvanic current to re-assemble the particles 

 of copper from a solution, and make them again into a solid 

 plate the rending force of the thunderbolt as it strikes the 

 oak. See also how both heat and light observe the angle of 

 incidence in reflection, as exactly as does a stone thrown 



