510 THE SENSORIAL FUNCTIONS. 



confines of the two great departments of human 

 knowledge, (of which the one relates to the 

 phenomena of matter, and the other to those 

 of mind,) requires for its successful cultivation 

 the combined efforts of the physiologist and 

 the metaphysician. For although our sensa- 

 tions are purely mental affections, yet inasmuch 

 as they are immediately dependent on physical 

 causes, they are regulated by the physical laws 

 of the living frame ; whereas the perceptions 

 derived from these sensations, being the results 

 of intellectual processes, are subject rather to 

 the laws which regulate mental than physical 

 phenomena. It is certain, from innumerable 

 facts, that in the present state of our existence, 

 the operations of the mind are conducted by the 

 instrumentality of our bodily organs ; and that 

 unless the brain be in a healthy condition, these 

 operations become disordered, or altogether 

 cease. As the eye and the ear are the instru- 

 ments by which we see and hear, so the brain 

 is the material instrument by which we retrace 

 and combine ideas, and by which we remember, 

 we reason, we invent. Sudden pressure on this 

 organ, as in a stroke of apoplexy, puts a total 

 stop to all these operations of the mind. If the 

 pressure be of a nature to admit of remedy, 

 and has not injured the texture of the brain, 

 recovery may take place; and immediately on 

 the return of consciousness, the person awakes 



