260 RELATIONS OF PHYSIOLOGY TO METAPHYSICS. 



of positive investigation have been repudiated. If from the construction 

 of the human brain we may demonstrate the existence of a soul, is not 

 that a gain? for there are many who are open to arguments of this 

 class, on whom speculative reasoning or a mere dictum fall without any 

 weight. Why should we cast aside the solid facts presented to us by 

 material objects ? In his communications throughout the universe with 

 us, God ever materializes. He equally speaks to us through the thou- 

 sands of graceful organic forms which are scattered in profusion over the 

 surface of the earth, and through the motions and appearances presented 

 by the celestial orbs. Our noblest and clearest conceptions of his attri- 

 butes have been obtained from these material things. I am persuaded 

 that the only possible route to truth in mental philosophy is through a 

 study of the nervous mechanism. The experience of 2500 years, and 

 the writings of the great metaphysical intellects, attest with a melancholy 

 emphasis the vanity of all other means. 



Whatever may be said by speculative philosophers to the contrary, 

 the advancement of metaphysics is through the study of physiology. 

 What sort of a science would optics have been among men who had pur- 

 posely put out their own eyes ? What would have been the progress of 

 astronomy among those who disdained to look at the heavens ? Yet that 

 is the preposterous course which has been followed by the so-called phi- 

 losophers. They have given us imposing doctrines of the nature and 

 attributes of the mind, in absolute ignorance of. its material substratum. 

 Of the great authors who have thus succeeded one another in ephemeral 

 celebrity, how many made themselves acquainted with the structure of 

 the human brain ? Doubtless some had been so unfortunate as never to 

 see one ! yet that wonderful organ was the basis of all their speculations. 

 In voluntarily isolating themselves from every solid fact which might 

 serve to be a landmark to them, they may be truly said to have sailed 

 upon a shoreless sea from which the fog never lifts. The only fact which 

 they teach us with certainty is that they know nothing with certainty. 

 It is the inherent difficulty of their method that it must lead to unsub- 

 stantial results. What is not founded on a material substratum is nec- 

 essarily a castle in the air. 



Returning now to the general description of the nervous mechanism, 

 and following the division above indicated, we shall consider, first, the 

 fibrous element of the nervous system, and, second, the vesicular. 



First. Of the fibrous there are two varieties, one belonging to the 

 Fibrous or tu- cerebro-spinal, and the other to the sympathetic. The for- 

 buiar portion. mer mav -fo Q described as a delicate membranous tube contain- 

 ing a semi-fluid material, and presenting under the microscope a pellucid 

 glassy appearance when examined in the recent state ; a spontaneous 

 separation or partition, however, soon ensues, a white material or medul- 



