CHAPTER IV.

GENERAL DIFFERENCES OF THE TWO LIVES WITH RESPECT TO DURATION OF ACTION.

One of the great distinguishing characters of the phenomena of the animal life in opposition to those of the organic life, has just been shewn. That, which I am about to examine, is not of less importance. The functions of the animal life intermit; the functions of the organic life are performed with an uninterrupted continuity.

I. _Of continuity of action in the organic life._

Prolong but little the causes which are capable of suspending respiration, or the circulation of the blood, and life itself shall be suspended, nay, even annihilated. All the secretions go on uninterruptedly; if they intermit at all (and those of the bile and saliva for instance, when not immediately required for the purposes of digestion and mastication, may be said to intermit) such intermissions affect the intensity of the secretion only, and not the entire exercise of the function. Exhalation and absorption incessantly succeed each other; the process of nutrition must be continually carried on; the double movement of assimilation and decomposition from which it results, can only be terminated with life itself.

In this concatenation of the organic phenomena, each function depends immediately upon those which precede it. The centre of them all, the circulation, is immediately connected with the exercise of them all, for when this is troubled, they languish, when this ceases, they cease also. Just in the same manner the movements of a clock all stop with the pendulum. Nor only is the general action of the organic life connected with the heart; but there cannot exist a single function of this nature unconnected with all the others, for without secretion, there can be no digestion, without exhalation no absorption, without digestion no nutrition. Hence as a general character of the organic functions may be indicated continuity of action, and mutual dependence.

II. _Of intermission of action in the organic life._

In the exercise of the functions of the animal life, there will be regularly seen an alternation of activity and repose, complete intermissions, and not remissions only.

Fatigued by long continued action, the senses all alike become for a time, incapable of receiving any further impression. The ear loses its sensibility to sound, the eye to light, the tongue to savours, the pituitary membrane to smells, the touch to the qualities of bodies about which it is conversant, and all this for the sole reason that the respective functions of these different organs, have for a long time been exercised.

In like manner, the brain fatigued by too great an effort in the exercise of any of its powers, in order to regain its excitability, must cease to act for a period proportioned to the duration of its preceding action. The muscles also after having been strongly contracted, before they can contract anew, must remain for awhile in a state of relaxation. Hence in locomotion, and the exertion of the voice, there must be intermissions.

Such then is the character peculiar to the organs of the animal life. They cease to act because they have acted. They become fatigued, their exhausted powers must be renewed.

This intermission is sometimes general, sometimes partial. When a single organ, for a long time has been exercised, the others remaining inactive, it relaxes and sleeps, the others continuing to watch.--Hence, without doubt, proceeds the reason, why there is no immediate dependence among the functions of this order on each other. The senses being shut up against sensation, the brain may still subsist in action, may remember, imagine, or reflect. In such case the power of locomotion and the voice also, may equally well be exercised, and these in like manner may remain unexercised, and the activity of the senses be in no-wise impaired.

Thus the animal at will may fatigue any one of the parts of this life, and on this very account, such parts must all of them possess a capability of being relaxed, a power of repairing their forces in an isolated manner. This is the partial sleep of the organs.

III. _Application of the law of intermission of action to the theory of sleep._

General sleep is the sleep of all the parts. It follows from that law, which with respect to the functions of the animal life, enchains intermission with periods of action, from that law, by which this life is particularly distinguished from the organic life.

Very numerous varieties are remarked in this periodical state, to which all animals are subject. The most complete sleep is that in which the outward life is entirely suspended. The least perfect sleep is that which affects one organ only; it is that of which we have just been speaking.

Between these two extremes there are many intermediate states. At times perception, locomotion, and the voice only are suspended; the imagination, the memory, and the judgment remaining in action. At other times, to the exercise of the latter faculties are added those of the locomotive organs and the voice.--Such is the sleep, in which we dream, for dreams are nothing more than a portion of the animal life escaped from the torpor, in which the other portion of it is plunged.

Sometimes but very few of the senses have ceased their communication with external objects. Such is that species of somnambulism, in which to the action of the brain, the muscles, and the larynx, are added the very distinct actions of the ear and the sense of touch.[13]

Sleep then cannot be considered as a constant and invariable state with regard to its phenomena.--Scarcely ever do we sleep in the same manner twice together. A number of causes modify in applying to a greater or less portion of the animal life the laws of intermission of action. Its different degrees should be marked by the different functions, which these intermissions affect.

But the principle of it is every where the same from the simple relaxation of a muscle to the entire suspension of the whole of the animal life. Its application, however, to the different external functions, varies without end.

These ideas on sleep are different, no doubt, from that narrow system, where its cause exclusively placed in the brain, in the heart, in the large vessels, or in the stomach, presents an isolated and frequently an illusory phenomenon, as the base of one of the great modifications of life.

And what is the reason why light and darkness in the natural order of things, coincide so regularly with the activity or intermission of the external functions? The reason is this, that during the day a thousand means of excitement perpetually surround the animal, a thousand causes exhaust the powers of his sensitive and locomotive organs, fatigue them, and prepare them for a state of relaxation, which at night is favoured by the absence of every kind of stimulus. Thus, in the actual state of society, where this order is in part inverted, we assemble about us at evening, a variety of excitants, which prolong our waking moments, and put off until towards the first hours of daylight, the intermission of our animal life, an intermission, which we favour besides by removing from the place of our repose whatever might produce sensation.

We may for a certain time, by multiplying the causes of excitement about them, withdraw the organs of the animal life from this law of intermission, which should naturally cause them to sleep; but at last they must undergo its influence, and nothing can any longer suspend it. Exhausted by watching, the soldier slumbers at the cannon’s side, the slave under the whip, the criminal in the midst of torture.

We must carefully make a distinction, however, between the natural sleep, which is the effect of lassitude, and that, which is the consequence of some affection of the brain, of apoplexy, or concussion, for instance. In the latter case the senses watch, receive impressions, and are affected as usual, but these impressions are not perceived by the diseased sensorium; we cannot be conscious of them. On the contrary, in ordinary sleep the senses are affected as much, or even more than the brain.

From what has now been said, it follows, that the organic life, has a longer duration than the animal life. In fact the sum of the periods of the intermissions of the latter, is almost equal to that of the times of its activity. We live internally almost double the time that we exist externally.

FOOTNOTE:

[13] The action of the brain is far from being preserved in somnambulism. The thread of ideas, on the contrary, is completely broken, and this is the most striking character which distinguishes every kind of sleep from wakefulness. The mind then cannot reflect upon the sensations which it receives, it abandons itself successively and without any resistance to all those which are presented, without examining the connexion which they can have between them. In ordinary sleep, the senses are almost entirely blunted, the mind receives no other sensations than those which have been derived from memory; but they present themselves in a confused manner, without order and in such a way as often to form the most strange and incoherent images. In somnambulism the action of many senses, and that of hearing in particular is preserved; the judgment of the sleeper can then exercise itself not only upon its reminiscences, but also upon the impressions which are transmitted to it from without. The sound of a bell or a drum, being heard while we are in a dream, will immediately modify it. In this way a person may gain the attention of a somnambulist, and as the latter possesses the use of his voice, it will be seen by his answers that his ideas can be directed at will, and led in this way wherever it is wished; for the impressions that he receives from without, being stronger than those which come from memory, he will almost always obey the first.