166 



ON THE EXTERNAL SENSES 



more sensible to pain than the lungs, the brain, or the stomach ; but even the 

 skin itself is more sensible in some parts than in others, which are appa- 

 rently supplied with an equal number of nerves, and of nerves from the very 

 same quarter. It is perhaps least sensible in the gums ; a little more so on 

 the hairy scalp of the head ; much more so on the front of the body ; and most 

 of all so in the interior of the eyelids : while the bones, teeth, cartilages, 

 cuticle, and cellular membrane, though largely supplied with nerves, have no 

 sensation whatever in a healthy state. 



As the degree of intelligence decreases, we have reason to believe that the 

 intensity of touch or corporeal feeling decreases also, excepting in particular 

 organs, in which the sense of touch is employed as a local power. And 

 hence we may reasonably conjecture that in some of the lowest ranks of ani- 

 mals, the sensibility may not exceed, even in their most lively organs, the 

 acuteness of the human cellular membrane, cuticle, or gums. 



This, however, does not rest upon conjecture or even upon loose indefinite 

 reasoning. We find in our own system that those parts which are most inde- 

 pendent of all the other parts, and can reproduce themselves most readily, 

 are possessed of the smallest portion of sensation ; such are all the appen- 

 dages of the true skin, the cuticle, horn, hair, beard, and nails : some of which 

 are so totally independent of the rest, that they will not only continue to live, 

 but even to grow, for a long time after the death of every other part of 

 the body. 



Now it is this very property by which every kind of animal below the 

 rank of man is in a greater or less degree distinguished from man himself. 

 All of them are compounded of organs which in a greater or less degree ap- 

 proach towards that independence of the general system which, in man, the 

 insensible or less sensible parts alone possess ; and hence all of them are 

 capable of reproducing parts that have been destroyed by accident or disease, 

 with vastly more facilitj'^ and perfection than mankind can do. 



I have once or twice had occasion to apply this remark to the lobster, 

 which has a power not only of reproducing its claws spontaneously, when 

 deprived of them by accident or disease, but of throwing them off sponta- 

 neously whenever laid hold of by them, in order to extricate itself from the 

 imprisoning grasp. The tipula pectiniformis, or insect vulgarly called father- 

 long-legs, and several of the spider-family, are possessed of a similar power, 

 and exercise it in a similar manner. These limbs are renewed by the forma- 

 tive effect of the living principle in a short period of time : but it would be 

 absurd to imagine that in thus voluntarily parting with them the animal puts 

 himself to any very intolerable degree of pain ; for in such case he would not 

 exert himself to throw them off. The gad-fly, when it has once fastened on 

 the hand, may be cut to pieces apparently without much disturbance of its 

 gratification ; and the polype appears to be in as perfect health and content- 

 ment when turned inside out as when in its natural state. This animal may 

 be divided into halves, and each half by its own formative and instinctive 

 effort will produce the half that is deficient, and in this manner an individual 

 of the tribe may be multiplied into countless numbers. 



In many animals of the three classes of amphibials, insects, and worms, 

 the most dreadful wounds that can be inflicted, unless actually mortal, seem 

 hardly to accelerate death ; and hence we have a decisive proof that the pain 

 endured by such animals must be very considerably and almost infinitely less 

 than would be suffered by animals of a more perfect kind, and especially 

 by man ; since in these the pain itself, and the sympathetic fever which fol- 

 lows as its necessary result, would be sufficient to kill them independently 

 of any other cause. 



The life of man is in jeopardy upon the fracture or amputation of a limb; 

 and even at times when his body has been spattered over with a charge 

 of small shot, or only of gunpowder. But M. Ribaud, with a spirit of expe- 

 rimenting that I will not justify, has struck different beetles through with 

 pins, and cut and lacerated others in the severest manner, all of which lived 

 through their usual term of life as though no injury had been committed on 



