72 Darwinism and Other Essays. 



ments in tissue in muscular tissue, in adipose, 

 in cellular, and in nerve tissue, and so on. Every 

 undulation that takes place among the molecules 

 of a nerve represents some simpler form of molec- 

 ular motion contained in food that has been as- 

 similated ; and, for every given quantity of the 

 former kind of motion that appears, an equivalent 

 quantity of the latter kind disappears in producing 

 it. And so we may go on, keeping the account 

 strictly balanced, until we reach the peculiar dis- 

 charge of undulatory motion between cerebral 

 ganglia that uniformly accompanies a feeling or 

 state of consciousness. 



What now occurs ? Along with this peculiar 

 form of undulatory motion there occurs a feeling 

 the primary element of a thought or of an 

 emotion. But does the motion produce the feel- 

 ing, in the same sense that heat produces light ? 

 Does a given quantity of motion disappear, to be 

 replaced by an equivalent quantity of feeling? 

 By no means. The nerve-motion, in disappear- 

 ing, is simply distributed into other nerve-mo- 

 tions in various parts of the body, and these other 

 nerve-motions, in their turn, become variously 

 metamorphosed into motions of contraction in 

 muscles, motions of secretion in glands, motions 

 of assimilation in tissues generally, or into yet 



