124 AN INTRODUCTION TO SCIENCE 



power. All that we learn from experimental evidence is, 

 that afferent impulses are transmitted by the grey matter of 

 the central nervous system into efferent channels. 



Physiology has passed through the same stages as other 

 sciences, but, owing to the importance of its applications, 

 the stage of a priori reasoning has been unduly prolonged. 

 It began with few facts and much conjecture. As knowl- 

 edge accumulated untenable hypotheses were successively 

 abandoned ; but theories took their place, which, because 

 more detailed, appeared to be more true. Now it is enter- 

 ing a phase which, to borrow a term from religious contro- 

 versy, may be called agnostic. We have heard of the 

 automatic functions of nerve-cells, we have seen the ner- 

 vous system mapped out in a multitude of little centres and 

 offices, upon a strikingly anthropomorphic plan ; but now 

 physiologists are beginning to acknowledge that they do 

 not know of any function possessed by the nervous system 

 save that of redistributing the forces which are impressed 

 upon the body by the outer world. Truly, it has other 

 duties there is not the least doubt about that but we do 

 not know how it performs them. Not a glimmer of light 

 has been thrown into the mysterious recesses in which the 

 brain stores its presentations of sense. We know nothing 

 about the mechanism of memory, and memory is a neces- 

 sary antecedent to any action in which the brain shows 

 initiative. The work demanded of the brain is of three 

 orders, (i) It redirects impulses; (2) it stores impulses 

 and, therefore, when it sets them free again, it appears to 

 initiate them ; (3) it manifests the phenomena of con- 

 sciousness and volition which characterise or constitute the 

 ego. As yet experimental physiology has thrown no light 

 upon any process but the first. 



Turning to the handbooks of twenty or even ten years 

 ago, we find the elaboration of the nervous system carried 

 to great lengths. All tissues were supposed to manage the 

 daily business of repair and waste, production of an 



