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SCIENCE. 



SENSIBILITY AND ITS DIVERSE FORMS. 



By M. Oltramare. 



[Translated From the French, by the Marchioness Clara Lanza.] 



From the feeble cry by which the infant affirms simul- 

 taneously its birth and its sensibility, to the last long 

 drawn sigh which bids adieu to existence, human life 

 oscillates constantly between two opposite conditions 

 created by the nervous system— pleasure and pain, joy 

 and sorrow. 



Being creatures developed to a great extent under the 

 influence of the senses, we experience to an extreme de- 

 gree, the action of all exterior agents, and atone for such 

 pleasures as are granted to us by our exquisite sensibility, 

 with moral and physical suffering. Not satisfied with 

 momentary impressions, we foresee the influences which 

 are to reach us, and by means of our refined intelligence 

 we create those two great incentives to our actions — 

 apprehension and desire. 



Being mortal and also conscious of the fact, we natu- 

 rally have a presentiment of the final destruction of our 

 bodies, and most of us fear this and look upon it with 

 dread. Nothing of this kind, however, is to be met with 

 in animals. The last hour of life, brutal and violent 

 though it may be and totally unexpected, does not affect 

 them. The dog licks his master's hand affectionately 

 whether it be extended to caress or to kill. He is no 

 more conscious of the possibility of death, than is the ox 

 which is led to the slaughter house. 



These higher animals have nevertheless, a sensiblity 

 and individuality upon which their reason depends. They 

 possess what we call instinct. But, as we descend fur- 

 ther in the animal world, we see that this function gradu- 

 ally diminishes in proportion as the organisms become 

 simplified, until finally we reach a point, where to cut a 

 living creature in two, not only produces no perception ol 

 pain, but actually becomes a means of reproduction, each 

 half being capable of forming a distinct organism pre- 

 cisely like the original. 



Lower still, we come to plants, which are living organ- 

 isms, although Linnaeus, a naturalist of the highest rank, 

 refused to admit their sensibility. He says: " Plants live 

 and grow ; animals live, grow and feel." 



This theory recalls that of Aristotle, when the Grecian 

 philosopher affirmed that all organized beings had a soul 

 more or less developed. 



To the vegetable soul he attributed two faculties — 

 growth and reproduction. To the animal soul he as- 

 signed four faculties — growth, reproduction, sensibility 

 and motion. To the human soul, five faculties. The 

 four above mentioned, to which was added intelligence, 

 or mind. 



Neither Linnaeus nor Aristotle admit of any sensibility in 

 vegetable life, and yet this is as great an error as to deny 

 the existence of this same faculty in animals. An error, 

 which is almost universal even in the thinking world, and 

 which certainly should no longer be allowed to exisf. 

 From the most minute plant, to the most perfect animal, 

 we find sensibility under various forms, but always corre- 

 sponding to Claude Bernard's definition: " Sensibility is 

 the ensemble of all kinds of modifications, determined in 

 living things by different stimuli, or rather, the apti- 

 tude to reply to the provocation of these stimuli by- 

 means of modifications." 



Bichat distinguishes three forms of sensibility: 



1 . Conscious sensibility, which presides'over relations to 

 exterior movements. 



2. Unconscious sensibility, 'representing internal move- 

 ments. 



3. Insensible, or imperceptible sensibility, so called be- 

 cause it is manifested in other ways than by move- 

 ment. 



Putting aside these fine distinctions, let us admit two 

 forms of sensibility — conscious and unconscious — and we 

 shall be able to demonstrate the possibility of a passage 



from one state to the other, which proves that they are but 

 modifications of a single attribute. 



When we learn to read, it is with considerable diffi- 

 culty, and we doubt if any one ever mastered the art un- 

 consciously. But later, can we not peruse page after 

 page mechanically, without having an idea of their con- 

 tents? A transformation has therefore taken place in 

 two kinds of sensibility. It is precisely the same with 

 walking and many other acts in which the brain — that is 

 to say, the conscious agent — plays but a secondary 

 part. 



If I prick the foot of a frog with a needle the animal 

 draws it away, and, forewarned by the pain, endeavors to 

 escape. Sensibility here evidently assumes a conscious 

 form. If, however, I decapitate the frog, that is, if I de- 

 stroy the organ which is the ego, so to speak, and once 

 more perform my experiment, the mutilated body draws 

 the leg away, but makes no attempt to escape. The act 

 is purely reflex, unconscious, and in this case, by a simple 

 experimental artifice, I am able at once to substitute the 

 second form of sensibility for the first. 



We breathe without knowing it, without the interven- 

 tion of our will ; but if our attention is directed upon this 

 mechanical act, we become immediately conscious of 

 it. 



In eating, when once our food is swallowed we know 

 nothing more about it, and yet our sensibility is con- 

 stantly played upon by these substances, which, physic- 

 ally and chemically modified, are introduced into the 

 circulation of the blood, and thence carried to the ana- 

 tomical elements, whose sensibility they incite to action. 

 All vital properties, and, consequently, sensibility, reside 

 in those little numberless organic unities which go to 

 form living beings. 



There exists a fundamental matter, protoplasm, an amor- 

 phous substance endowed with peculiar properties and 

 which Huxley has justly termed the physical bas's of life. 

 This protoplasm, which sometimes alone constitutes an 

 inferior living creature, not only moves but attaches to it- 

 self minute particles which it mee's with in the water, 

 digests them and assimilates them with itself. Ether, 

 the great reagent of sensibility, causes it to lose its trans- 

 parency, and its movements to disappear. Then, when 

 it is evaporated, the fluid reappears with all the attributes 

 of this inferior life. This is undoubtedly sensibility, but 

 in an unconscious form. 



If we begin to mount the organic ladder, we see 

 gradually appear certain cells which specify sensibility, 

 and which, created solely to perform this function, elevate 

 and perfect it. These are the so-called nerve cells. 

 They are scattered throughout living organisms ; in the 

 higher animals they are very numerous, and serve to 

 centralize impressions and produce individuality. When 

 they are united to others called cephalic cells, they ad- 

 mit not only of sensation, but also the interpretation of 

 sensation which then becomes conscious. 



Thus, beginning with this infinite attribute of living 

 matter which Haller and Glisson, being too timid to call 

 sensibility, termed irritability, we gradually come to the 

 highest forms, whence originate the greater portion of 

 intellectual and physiological phenomena. 



In man, all the sensible nerve cells are united in one mass 

 called the cerebro-spinal axis, or the encephalo-medullary 

 mass. It is composed of the spinal cord, the medulla 

 oblongata, and the brain, each of its departments repre- 

 senting one form of sensibility. The spinal cord, prop- 

 erly speaking, corresponds to unconscious sensibility. 

 This is illustrated by that involuntary and spontaneous 

 movement which we call reflex action. The medulla ob- 

 longata controls sensations which, like respiration for in- 

 stance, are frequently unconscious, but which, however, 

 by an effort of the will, can be interpreted as precisely the 

 opposite. The brain possesses the highest form of sensi- 

 bility, and it is here that the greater part of our physical 

 and intellectual acts are performed. By means of the mi-' 



