OF THE EXISTENCE OF THE SOUL. 283 



external world are the sensory ganglia and the cerebral Evidence of the 

 hemispheres. We may now profitably inquire whether any existence of the 



j. -u i, if f ^ t. soul derived 



argument in behalf of the existence of such an agent may f r0 m cerebral 

 be gathered from the anatomical and physiological facts just structure - 

 presented, or whether we must assume it as a postulate, relying for proof 

 on evidences of a totally different character to those which are presented 

 by the science now engaging our attention. It is to be greatly regretted 

 that evidence drawn from structural arrangement has hitherto, by very 

 high authority, either been totally cast aside or held in very light esteem. 

 It is still more deeply to be regretted that those who should have known 

 better have conceded the argument that from no consideration based 

 upon anatomical or structural arrangement could proof be obtained of 

 the existence of an immaterial principle. Even by such, the study of 

 physiology has been designated as leading to materialism, and, with an 

 injustice which can not be too emphatically reprobated, the scandal has 

 often been quoted, that where there are three physicians there are two 

 atheists. 



But what if it should turn out that, from the study of the cerebral 

 mechanism, distinct proof can be obtained on this point proof of just as 

 cogent a nature in support of the doctrine of the existence of the soul 

 as that which we have of the existence of the external world, and of pre- 

 cisely the same character? Without, therefore, occupying -myself with 

 such other evidence as might be drawn from theological or metaphysical 

 sources, and which are therefore extraneous to the object of this work, I 

 shall proceed to point out such considerations as naturally offer them- 

 selves to our minds when we recall the general structure of the nervous 

 apparatus. Eepeating, therefore, such facts as may be necessary for the 

 proper understanding of this interesting argument, I present it as follows : 



The simple cellated nervous arc consists essentially of these portions, 

 a centripetal fibre, a vesicle, and a centrifugal fibre ; the cen- Automatic 

 tripetal fibre may have at its outward or receiving extremity mechanism of 

 vesicular or cellular material. Thus constituted, this mech- 

 anism is ready to receive external impressions, which, if such language 

 may be appropriately used, are converted or reflected in part by the gan- 

 glion into motions, and the residue retained. But the arc, viewed by it- 

 self, is a mere instrument, ready, it is true, for action, but possessing no 

 interior power of its own. It is as automatic as any mechanical con- 

 trivance in which, before a given motion can be made, a certain spring 

 must be touched. 



The essential condition of the activity of such a nervous arc is there- 

 fore the presence and influence of an external agent a some- Re uireg an 

 thing which can commence the primitive impression, for with- external agent 

 out it the mechanism can display no kind of result. More- for actlon * 



