vi.] ON THE STUDY OF ZOOLOGY. 93 



motion in the parts below the section is destroyed ; and on the 

 other hand, if, the cords remaining entire, the brain mass be 

 destroyed, the same voluntary mobility is equally lost. Whence 

 the inevitable conclusion is, that the power of originating these 

 motions resides in the brain, and is propagated along the nervous 

 cords. 



In the higher animals the phenomena which attend this 

 transmission have been investigated, and the exertion of the 

 peculiar energy which resides in the nerves has been found to be 

 accompanied by a disturbance of the electrical state of their 

 molecules. 



If we could exactly estimate the signification of this disturb 

 ance ; if we could obtain the value of a given exertion of nerve 

 force by determining the quantity of electricity, or of heat, of 

 which it is the equivalent; if we could ascertain upon what 

 arrangement, or other condition of the molecules of matter, the 

 manifestation of the nervous and muscular energies depends, 

 (and doubtless science will some day or other ascertain these 

 points,) physiologists would have attained their ultimate goal in 

 this direction ; they would have determined the relation of the 

 motive force of animals to the other forms of force found in 

 nature ; and if the same process had been successfully performed 

 for all the operations which are carried on in, and by, the animal 

 frame, physiology would be perfect, and the facts of morphology 

 and distribution would be deducible from the laws which physio 

 logists had established, combined with those determining the con 

 dition of the surrounding universe. 



There is not a fragment of the organism of this humble 

 animal whose study would not lead us into regions of thought 

 as large as those which I have briefly opened up to you ; but 

 what I have been saying, I trust, has not only enabled you to 

 form a conception of the scope and purport of zoology, but has 

 given you an imperfect example of the manner in which, in my 

 opinion, that science, or indeed any physical science, may be 

 best taught. The great matter is, to make teaching real and 

 practical, by fixing the attention of the student on particular 



