CHAPTER III. 



OF PHYSICAL SENSIBILITY AND THE MECHANISM OF 

 SENSATIONS. 



How are we to conceive that certain parts of a living body can possess 

 the faculty of feeling, when no kind of matter whatever does or can 

 enjoy any such faculty ! 



It was indeed a great mistake to imagine that animals, even the most 

 perfect, were endowed with feeling in certain of their parts. Assuredly 

 the various humours and fluids of living bodies can no more possess 

 the faculty of feeling than the solid parts. 



It is only by a real hallucination that the separate parts of our body 

 appear to be sensitive ; for it is our entire being that feels or rather 

 undergoes a general effect, on the stimulus of some affective cause. 

 Since this effect is always referred to the part affected, we promptly 

 derive from it a perception to which we give the name of sensation ; 

 and we are misled into the belief that it is the affected part of our 

 body that feels an impression, whereas it is a commotion throughout 

 the entire sensitive system which conveys to that part its general 

 effect. 



These considerations may appear strange and even paradoxical, 

 for they are far removed from the common opinion on this subject. 

 Yet if the reader will suspend his judgment until he has examined the 

 grounds on which I base my opinion, he will doubtless abandon the 

 idea of attributing the faculty of feeling to any individual part of a 

 living body. But before stating my views, it must first be determined 

 what animals possess the faculty of feehng and what animals have no 

 such faculty. 



Let me first enunciate the following principle : Every faculty possessed 

 by animals is necessarily the product of an organic act and consequently 

 of some movement ; if the faculty is special, it results from the function 

 of some special organ or system of organs ; but no part of the animal 

 body that remains motionless could possibly give rise to any organic 



