53 MEMORIAL SKETCH 



All this I have developed in my " Comparative Physiology " 

 — not as fully, however, as I could wish. But I have there 

 avoided touching on the relation of Mental force to those 

 commonly called Material. I have been turning the matter 

 over in my mind, however, and have come to the conclusion that 

 we cannot logically separate them. It is all very well to say 

 that Mind and Matter are distinct entities ; but we are talking of 

 forces, not of material substances, and I cannot see any reason 

 for shrinking from the conclusions to which the facts appear to 

 point. These conclusions you will find in the enclosed note to 

 a friend, whose opinion I much desired. In addition to what I 

 have said there of the action of the mind upon the body, I 

 might advert to the influence of emotional states in modifying 

 the nutrition and secretion, and conversely to the marvellous 

 influence of a slight contamination of the blood on the emotional 

 states. 



To Dr. Paget. 



I have been thinking much more about Mental phenomena, 

 and have been questioning within myself whether Mental force 

 should not be brought into the general category of the Vital 

 forces, on the grounds that Nervous force excites Mental force 

 (as in sensation giving origin to Mental operations), and con- 

 versely Mental force excites Nervous force (as in emotional or 

 volitional actions). It seems to me impossible to deny that 

 this correlation is as complete as those existing among the 

 physical forces ; whatever we may think of the degree in which 

 the higher phenomena of mind are dependent upon material 

 conditions. Further, Nervous force is, in the animal body, that 

 kind of connecting link between Mental force and the Physical 

 forces which Electricity (as Grove has shown) often is among 

 the Physical forces themselves, one being often convertible into 

 another through the medium of electricity, which is not thus 

 convertible directly. But if such a correlation really exists 

 between Mental and Vital and Physical forces, that the one 

 may even indirectly produce the other, may we not regard all 

 the physical forces of the universe as the direct manifestation of 

 the Mental force of the Deity ? I believe that I could find 

 very orthodox testimony in support of some such view. Locke 



