74 NATURE AND LIFE. 



ated at other poles, and which combine with the first in ex- 

 citing in their turn new impulses. Such are the chief 

 noticeable ways in which innervation makes its appearance 

 and fulfills its action ; a property which, rudimentary, and 

 hardly to be detected in the lower animals, rises in the 

 higher ones, and lifts them, too, to so lofty a degree of 

 perfection. Whatever may be, as to the rest, the first 

 cause of the most striking acts of our life, of the affections 

 and the intellect, we feel, will, imagine, and understand, 

 only through the means of these nerve-corpuscles distrib- 

 uted through cur system, and endowed with that power, 

 not paralleled elsewhere, of receiving, transmitting, per- 

 ceiving, storing away, and modifying impressions. 



This, then, is one first and fundamental lesson yielded 

 by the study of the anatomical elements ; the play of ani- 

 mal organisms is reduced to four simple essential modes of 

 action : nutrition, evolution, contractility, and innervation. 

 At once distinct and combined, sometimes intricately in- 

 termingled, sometimes visibly separate, consubstantial with 

 those anatomical elements by which their existence is made 

 known, capable of putting on various and manifold ap- 

 pearances, these properties are the springs of all living 

 mechanisms. In machines produced by man's industry, 

 one single force goes through many forms to accomplish 

 the most various effects. In animals, several different forces 

 have for their business, in the midst of a thousand entan- 

 glements and intricacies, to insure the perpetuation of the 

 species through the full working of the individual. 



We are thus led to speak of the generation of the ana- 

 tomical elements. This question is one of twofold gravity : 

 In the first place, it abounds in difficulties of every kind, 

 so extremely subtile are the observations in the case, so 

 prompt the senses to be misled, so ready the mind to be. 

 deceived. Then it borders on the most formidable prob- 

 lems, not merely of general anatomy, but also of naturul 



