288 The Scottish Naturalist. 



the general tactile sense. But then, in the first place, all the 

 senses are but modifications of touch. In the second place, in 

 Dr. Carpenter's sensori-motor action, the passage of the ingoing 

 molecular movement into the outgoing is equally immediate as 

 in the case of the reflex action. There may be an image in the 

 eye and a sound, or air-vibrations at least, in the ear ; but it is 

 not the image taken up as a mental one nor the vibrations of 

 the air taken up as a mentally perceived sound or tone — it is 

 neither that causes the outward response. This is caused by 

 the simple impact — by the touch of the light on the retinal 

 nervous structures, and the touch of the agitated air on the 

 terminal bodies of the nerves of the cochlea respectively. 

 If it were otherwise, if mental elements intervened, they could 

 intervene only in the shape of sensuous apprehension, imagina- 

 tion, or emotion, or idea ; and then where would be the 

 difference between sensori-motor and ideo-motor or emotional 

 reflection ? What we should on general principles presume is 

 what the actual parts of the case clearly bear out — that there 

 are only two fundamentally distinct classes of reflexion, viz., 

 that in which mental elements do not intermediate the action, 

 and that in which they do intermediate it. The one is auto- 

 matic action of the organism ; the other is automatic action of 

 the psychical power and of the organism together. Carpenter 

 himself says sensori-motor action requires the impression on the 

 sense organ to be felt as a sensation. (Phys. of Mind, p. 82.) 

 So far as it does it is fundamentally different from excito-motor, 

 but not fundamentally different from ideo-motor or emotional 

 reflexion. Des Cartes plainly included sensori-motor action in 

 the reflex action by which he explained the psychical pheno- 

 mena of animals. After speaking of movements in us that do 

 not depend on the mind, such as the action of the heart and 

 lungs, he goes on — " And when one who falls from a height 

 throws forward his hands to save his head it does not depend 

 upon his mind, but takes place merely because the senses being 

 affected by the present danger some change arises on his brain 

 which determines the animal spirits to pass thence into the 

 nerve in such a manner as is required to produce this motion 

 in the same way as in a machine, and without the mind being 

 unable to hinder it. Now," he adds, " since we observe this 

 in ourselves, why should we be so much astonished if the light 

 reflected from the body of a wolf into the eye of a sheep has 

 the same force to excite in it the motion of flight." (Cited by 



