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found a royal road to the sciences, and must be possessed of a mode of intelligence that has no parallel in humanity. It is this imitation of our higher mental processes by creatures apparently not capable of such processes according to our method that has constituted the chief difficulty and the standing wonder of animal instinct. There is required a very strict analysis both of human and of brute capacity to obtain if possible some deeper foundations of agreement such as will reconcile these anomalies. We are not at liberty to take for granted the existence of a wholly distinct mechanism of thought and activity in those remarkable individuals of the inferior creation till we have seen the uttermost that can be accomplished by the mechanism common to them and us. Taking our stand upon the universal susceptibilities and modes of action of the animal nature, we are bound to inquire what effects may be produced by the exaltation or depression of one or more of these, or by those changes in degree that nature makes in so great abundance without departing from the sameness or unity of the general type.
We have made special allusion in the foregoing remarks to the researches that have established the rigorous similarity (or 'homology,' as it is called) of the vertebrate skeleton. Between the vertebrate animals and the sub-kingdoms of mollusca, articulata, and radiata, no such scientific law of unity has been traced. Nevertheless, there is apparently a very great amount of similarity, and in all probability the greatest that could exist between forms and modes of life so diverse as theirs. The functions of digestion, circulation, respiration, secretion, and excretion maintain a common form so far as it is admissible in the altered structure of the individual. The instruments of locomotion, the organs of sense, the nervous system, still keep up an analogy in the midst of diversity; indeed, creatures that have to live on the same planet must be analogous in some degree; the permissible variety must depend solely on the variety of that planet's surface and constituents—it being one thing to walk on the solid earth, another to float in the waters, and something quite different to burrow under ground. Now, so far as the general outline of each creature and the manner of its subsistence will allow, we find that a common plan of mechanism is observed; and we therefore can do nothing better than to extend our sympathies and our modes of reasoning to the remoter types of animal life, in so far as we see them actuated with impulses analogous to our
There is no other point of view that we, as human beings, can take towards the shell-fish, the worm, or the insect, than what we adopt for quadrupeds, birds, or reptiles. Our humanity and our science alike demand this universal recognition of relationship.
In the subsequent detail of the present Paper our arrangement will be as follows:
1. The ANIMAL INSTINCTS, or the inborn capacities belonging to the universal type of the animal nature.
II. ANIMAL INTELLIGENCE, or the indications of intellect, and the means of acquired capacity among the animal tribes.
III. A view of some of the more prominent types of Animal CHA
IV. The remarkable instances of COMBINING or CONSTRUCTIVE POWER exhibited among the lower orders of creatures.
THE ANIMAL INSTINCTS.
In treating of the various susceptibilities and active capacities of the animal frame that are to be considered as native, or growing out of the original constitution of the individual, we must advert first to the class of feelings termed Sensations. These are to be looked upon as the foundation and starting-point, as well as the motives of activity. If by sensations we understand only the impressions and feelings made on the five senses, it will be requisite for us to notice an additional class of animal susceptibilities, as preliminary to the consideration of the instinctive actionsnamely, the class of appetites or impulses to action originating in different parts of the system. Our exposition will, therefore, have to embrace the Sensations, Appetites, and inborn Activities of the Animal nature.*
Animal Senses. The five senses commonly spoken of as belonging to man and to the higher orders of the brutes, are admitted to be a defective classification of the primary sensibilities of the animal frame. Not only do they omit the extensive class of feelings reflected from the muscular apparatus of the body, but they pass over the important sense of digestion, and of the various other operations of the alimentary canal. The feeling of taste located in the tongue and palate is a mere preliminary to the far more impressive volume of sensation resulting from the processes subsequently taking place upon the food. There are, not including the muscular feelings, at least seven distinct kinds of sensations, having all the commonly recognised characters of such. The superior animals rejoice, along with man, in the possession of seven senses.
It is very important for our present object to recognise distinctly at the outset the full compass of the mechanism entering into each of the senses-à mechanism that could never have been ascertained but for the recent discoveries in nervous anatomy. The supposition formerly entertained respecting sensation, was to the effect that an impression made on the eye or ear was carried into the brain and deposited in a sensorium or storehouse of sensations, whence it emerged afterwards as a recollection or some other species of thought. Such a doctrine is wholly at variance with the structure of the brain, as well as a fatal stumbling-block in the way of all clear knowledge of mental workings. There is no such thing as a cerebral closet or receptacle of imagery; the machinery of the nervous system is formed on a totally different plan--a plan, too, that when once revealed by anatomical investigation, agrees far better with the common experience and observation of mankind than the other hypothesis. Looking at the structure of the nervous system, we find it to consist of an apparatus arranged in a circular form--that is, returning to itself, somewhat after the analogy of a voltaic battery. At one part of the circle we find a ganglion or knot of nervous matter, highly vascular-in other words, abounding with minute
* See • Information for the People,' vol. ii. No. 71, where the human mind is treated of in a manner nearly parallel to the exposition of the animal mind in general, given in the present Paper.
bloodvessels -and from each ganglion proceed two sets of nerves, one terminating in an organ of sense, the other in some organs of motion. A circle is formed of these parts in the following order, beginning at the origin of the sensation: a sensitive surface; a nerve arising in it and proceeding inwards to a certain ganglion; the ganglion itself; and lastly, a nerve issuing from the ganglion towards a moving organ, and terminating in its muscles. If, for example, we take the sense of touch: the parts of the circle are—the integument of the fingers; the nerves proceeding from this integument to the ganglionic centre appropriated to touch; the ganglion itself; the efferent or outgoing nerves of the ganglion, of which a certain number at least proceed to the fingers themselves, or to the muscles that move them. Such is the fundamental structure of the nervous anatomy; and next, as to its mode of working.
When a stimulus is applied to any sensitive surface-to the tips of the fingers, for example—this stimulus immediately tells upon the fibres of the nerve embedded in that surface. The nerve-fibres have for their special function the communication or transmission of any influence brought to bear upon their extremities—they are what is termed conductors. The pressure exerted upon the nerves of touch when the fingers are squeezed is rapidly conveyed in some shape or other to the ganglion of the sense of touch; it is not swallowed up or stifled there, but as a part of its nature it acts upon the vascular globules or vesicles of the ganglion, influencing the circulation of the blood of those vesicles, and developing a motive-force which issues along the outgoing nerves, and is transmitted to the muscles of the fingers, or the parts affected by the sensation. This, and nothing less than this, constitutes a complete act or operation of sense. The original stimulus in the sentient surface always tends to produce a reflex stimulus of the organ that carries that surface. This movement will be either a movement of closer contact with the thing or object of sensation, or å movement of repulsion and retraction of the member, in case of the stimulus being painful or disagreeable. Put a ball in a child's open hand, and the effect of the touch will be, through the steps above described, to clench the hand and grasp the ball. If it is hot, or cold, or prickly, or in any way uncongenial to the organs, a different set of muscles will be communicated with and complete the round, and the hand will be rapidly withdrawn from the unwelcome touch. Until one or other of these two effects have been produced, the sensation cannot be said to have accomplished its natural
If a stimulus or impression from without stops short at the ganglionic centre, the fact shews either that the impression is feeble, that the ganglion or outgoing nerve is paralysed, or that some other stimulus of a more powerful kind and of a contrary nature has found its way to the same ganglion—a thing that often takes place in the complex organisation and multiplied communications of the nervous system.
In our search into the causes of the motive-power of the animal body, this view of the nature of sensation is all-important. It reveals to us at once a direct and unfailing connection between sense and activitythe two being only different portions of the same mechanism. A sensation is never complete till it brings forth an action. The permanency of the sensation as a recollected or revivable impression depends on its having had full scope and effect upon the moving organ concerned in the case.
The circulation of a nervous current, or propagation of a nervous vibration, whose nature is unknown to us, constitutes the entire fact of the sensation taken by itself: when this current or vibration has ceased there would appear to be no feeling present—no manifestation of sense any more than of movement. When we retrace a past sensation, we apparently do nothing beyond reviving the current of excitement between the sensitive surface and the moving part of the sensational circle.
Keeping in view, therefore, this relation between sensation and action, as between parts of the same whole, we will now pass in review the different classes of animal sensibilities, adverting in each instance to the special movements generated by the inherent activity of the circles of sense. We shall thus ascertain what amount of active power nature has associated with the very fact of sensibility, and shall thereby provide an adequate explanation of a certain fraction of the phenomena now under consideration.
1. Sensations of Organic Life.—It is necessary for us to recognise a class of feelings arising from the general well or ill being of the system at large as something distinct from the feelings of the special senses. Accordingly, physiologists have singled out those feelings under the name of general sensibility. The various processes at work in the waste and renovation of the tissues of the system give forth an influence upon
the consciousness, and make part and parcel of the happiness or misery of the individual existence.
The circulation of the blood, the respiratory action in the lungs, the secretions and excretions, the formation of new cells, and the absorption of decayed matter, seem all to give a certain amount of indication of their working, without in general drawing any special attention towards themselves. It is reckoned a criterion of good health to be utterly unconscious of any one of these processes ; and the maxim is so far true, for it is only in case of some disorder that the consciousness is strongly acted on by the organic processes of the system. But yet the vigorous action of the nutritive functions of the frame, and the purgation from every kind of waste matter, tell powerfully upon the whole state of feeling of the individual, bý enhancing the pleasure of existence, and rendering more vivid all the special senses and susceptibilities of the being. On the other hand, disease, laceration, insufficient nutriment, loss of repose, exhaustion, or any cause tending to interrupt the work of renewal and waste—the stream of vitality—make themselves felt by the same class of nerves, and produce a painful and irritated consciousness, whose influence overshadows all the other regions of conscious existence.
The obscurity that hangs over the nervous mechanism of organic sensibility must necessarily extend itself to the returning and motive portion of the nerve circles. The clearness and certainty of our knowledge of the complete round of the nervous current in the special senses do not belong to this more vague and diffused portion of our sensibility. This much we know, that when any part of the body becomes keenly conscious—in consequence of a painful disease, for example-there is a constant tendency kept up to move the part hither and thither, in the vain endeavour to withdraw it from the gnawing influence. In this tendency we can recognise the general fact of the reflex influence of the senses; for as a primary
law, it is seen that the returning nerves enter the muscles of the part affected, and the rebound of the sensation is shewn in either keeping up the sensitive part to the exciting object, or in retracting it, as the case may be. If the foot happen to be disordered and in pain, the muscles of the limb are kept in a constant state of solicitation to move the member about, and the utter uselessness of the attempt only adds to the irritation.
In the case of the breathing, which is one vital part of the organic system, every stimulus on the surface of the lungs reacts immediately on the muscles of respiration : the connection of action and sensation is here quite apparent. Pure air increases the rapidity of the breathing, impure air relaxes the energy of the breathing muscles ; and there is the same opposition between the effects of cold and warm air. As in the other senses, the reflex current of the respiratory sensations goes to the muscles controlling the sensitive organ—that is, the muscles of the chest.
There is one remarkable fact that goes to confirm the assumption now made as to the existence of sentient circles in all their completeness over every part of the body, for the purpose of making conscious the organic vitality of the system. This fact is no other than our sense of the direction or precise locality of any local irritation. In the human system the only means of indicating direction is by the movement of some member towards the place that may be in question. The movement of the eye tells direction in sight, and the movement of the hand tells the place of an object of touch. A point within the body which sends an impression towards the brain has its locality discovered by the stimulus given to the muscles adjoining the part, and by the movement thus set agoing. An uneasiness in the forearm is identified as to its place by the reflex action that it causes in the muscles of the forearm, and the movements consequent on this stimulus. In the interior of the abdomen, at a distance from any muscular actions, there is a great ambiguity and indistinctness as to the seat of a disordered feeling; and but for this tendency to reflect a stimulus upon the muscles nearest to the part, or the muscles carrying the part, we could not guess where the evil lay. There are artificial means of identifying the place of an acute organic sensation, by probing about till the sore gives evidence of being touched in the aggravated feel. ing of a new irritation; but nature's own method of indicating locality within the body is through the completion of each circle of sense by a muscular movement.
Inasmuch as the organic states of the body are affected by the atmospheric and other circumstances and conditions that surround it, the
rganic sibility is acted on by all these causes, and certain cognisance of external nature is the consequence. Changes of temperature alter the entire adjustment of the animal system: the rate of the breathing and of the circulation of the blood is changed, and many other alterations follow in train. So changes in the degree of moisture of the air affect the circulation, the action of the skin, and we know not how much besides; and some indication is given of this in the feelings of organic life. On the eve of a rain-storm, when the barometer falls, shewing a diminished pressure of the atmosphere, and when the air is getting charged with vapour to the point of saturation, the disturbance of the animal system is great and palpable. The human subject is generally conscious of an altered state of