This comparison with instinct will decidedly protect us, then, from regarding the immanent fitness of reflex movements as produced by conscious thought. The psychical autopsy of those reflex movements whose central organ is the brain entirely agrees with this; the first and last term of the psychical process, the perception of the stimulus, and the will to move fall within the consciousness of the organ, but not the uniting middle terms, which must contain the idea of design. The only mode of apprehending the matter, which is possible after our examination, is then this: that the reflex movements are the instinctive actions of the subordinate nerve-centres, i.e., absolutely unconscious presentations, which embody the will of the reflex action (conscious for the particular centre, but unconscious for the brain), in consequence of the perception of the stimulus. In addition to this perception in the reflecting centre, the stimulus can, by conduction, also be felt in the brain; but there is then a second perception, which has nothing to do with the, reflex movement and its occurrence. Instincts and reflex actions are also alike in this, that they exhibit essentially similar reactions in the individuals of the same animal species with similar stimuli and motives. This circumstance has given strength to the opinion that a dead mechanism is present instead of unconscious mental activity and immanent adaptation; but this circumstance as an objection to our view is invalidated by the consideration, that it is capable of an easy explanation in the manner indicated at the close of the chapter on Instinct.
1 Wagner’s Handwörterbuch der Physiologie, vol. ii. p. 542, article “Nervous Physiology,” by Volkmann. On the historical development of the notion of reflex movement. and for an estimate of the views of earlier investigators, which often come very near the truth, compare also the excellent memoir of J. W. Arnold: “The Doctrine of Reflex Functions.”
VI.
THE UNCONSCIOUS IN THE REPARATIVE POWER OF NATURE.
WHEN the nest of the bird, the web of the spider, the cocoon of the caterpillar, the shell of the snail are injured,—when the bird is stripped of a portion of its feathery robe,—the sufferers repair the loss which may imperil or impede their future existence. We have already seen that some of these phenomena must be ascribed to instinct, and can we fail to perceive the striking analogy of the other cases? We have seen that there is an unconscious idea of purpose, which, united with Will, dictates the conscious willing of the means to attain it; and are we to doubt that we have to do with the same thing, when the sphere of influence is no longer external, but the body itself, since we are not able to draw the line where the body proper begins and ends, as in the cocoon of the caterpillar, the shell of the snail, the feather-garment of the bird, or between excretion and secretion? If we deprive the polype of its tentacles or the worm of its head, the creature must die for want of food; and if the animal replaces the tentacles or the head and continues to live, can anything but the unconscious idea of their indispensableness be the fundamental cause of the restoration? Let it not be replied that the difference between instinct and the vis medicatrix lies in this, that in the former case the perceiving and willing of the means are, at any rate, conscious, but in the latter case these also are unconscious. For after the discussion on the independence of the lower nerve-centres, it cannot be doubted that the willing of the means may very well somehow and somewhere reach the stage of consciousness in the lower nerve-centres, e.g., the small ganglionic cells, from which the sympathetic nerve-fibres which regulate nutrition arise, even if the chief centre of the animal knows nothing at all about it. On the other hand, no one will confidently decide, whether and how far in the lower animals in the case of instinct even the willing of the means is a conscious act.
Let us now look a little closer at the effects of the vis medicatrix. In the case of the Hydræ every part of the mass is replaced, so that a new animal is formed out of each piece, whether the division be transverse or longitudinal, or the creature be even cut into shreds. Among the Planariæ every segment, if it only amounts to one-tenth or one-eighth of the whole body, becomes a fresh animal. Among the Annelids or worms restoration follows only after transverse section, when head or tail is always regenerated. In some cases the animal may be cut into pieces, and yet each single piece develops into a perfect example of its kind. It seems here clear enough that if, after any one of these indefinitely numerous sections, the separated part always furnishes a specimen manifesting the typical idea of its kind, this effect cannot be due to a dead causality, but the type-form must be present in each piece of the animal. But an IDEA can only exist either realiter in its external manifestation as realised idea, or idealiter so far as it takes the form of mental picture, and in and through the presentative act. Hence every fragment of the animal must have the unconscious image of the type according to which it accomplishes this regeneration; just as the bee before the construction of its first cell, and without ever having seen the like, carries in itself the unconscious representation of the hexagonal cell, accurate to half an angular minute, or as every bird must unconsciously have an idea of the form of the nest and mode of song characteristic of its species, before it has had any experience of the same. Andobserving the process of regeneration, e.g., of a divided earthworm, a white bud may be seen sprouting at the cut part, which gradually becomes larger, then acquires narrow, closely packed rings, expanding on all sides, and contains prolongations of the digestive canal, the vascular system, and the ganglionic cord. It requires a strong faith to suppose that the nature of the exudation at the wounded part and the vicinity of the corresponding organs are sufficient to bring about a further growth of the animal. But when one sees how from two similar cut surfaces, separated by several rings, there is formed on the one side the head with its special organs, on the other the tail with its organs, and with organs too which have nothing at all analogous in the remaining portion of the trunk, the assumption of a dead causality, of a material mechanism without an ideal factor, becomes a sheer impossibility.
In addition to this there are various secondary circumstances, which most clearly prove that the idea of what must be executed in the special case to realise the type is the originally determining element in these events. If the animal is not full-grown, and a part of it be violently removed, the regenerated part does not correspond to the former state of the animal, but is constituted as such part would have been had the normal process of development never been interrupted. This may be seen if the leg of a young salamander or the tail of a tadpole be cut off. Somewhat similar is the case of the horns of the stag, which are annually renewed as long as the youthful vigour of the animal remains; but when the development of the organism has reached its highest point and the vigour declines, the last pair of horns either remains till death, or the pair annually reproduced becomes in extreme age shorter and simpler.
Further, the force directed to this restoration of a part is greater the more important such part is for the continued existence of the animal: thus, e.g., according to Spallanzani, worms regenerate their heads before their tails, and in fishes the restoration of the amputated fins takes place in the order of their importance as motor organs; thus the caudal fins first, then the pectoral and ventral, and lastly the dorsal fins. Should the force, or more accurately the power, of the unconscious will in moulding its material and the external circumstances be insufficient for the regeneration of a part in the normal way, still the type of the class always gleams through the malformations which then arise. Thus, e.g., if only one tentacle instead of two grows again on a snail’s head which has been cut off, this one has two eyes, and men who have lost one joint of a finger sometimes have a nail growing on the second. The more a part is exposed to injury, the more easily is it regenerated. Thus, e.g., the rays of the Asterias, the legs of spiders, the tentacles and antennæ of snails and beetles, the tails of lizards, possess a considerable regenerative power on account of their liability to injury. For the most part, it is some special joint from which the regeneration most easily proceeds, in which case the connected limb is ext
remely fragile; and if injury occurs anywhere else, an additional limb is frequently thrown off at that spot. Crabs, for example, do this. Spiders likewise free themselves at the cost of a leg when they find it grasped or compressed; but if the animal be held fast whilst the leg is squeezed, it cannot afterwards thus unceremoniously throw off the same, but it first entangles the leg in its web, then propels itself with the other legs, and in this way wrenches it off. This is manifestly instinct; and when the crab spontaneously throws off the injured leg, is that to be called something fundamentally different from instinct? And yet rejection of the injured limb is merely the first act of restoration. Still more wonderful is the instinct of the Holothurise which live in the Philippine Islands of the South Sea. These devour coral sand, and if they be taken from their native haunts and transferred to clear sea-water, they of their own accord eject from the anus the intestinal canal, with the branchiæ and all other organs connected therewith, in order to form new viscera more in harmony with the altered medium. (A Holothuria burdened with needles or knives literally jumps out of its skin, rejecting it without in any way injuring its interior.)
The higher we ascend in the animal scale, the less potent, as a rule, becomes the vis medicatrix, being least influential in man. As long, therefore, as human physiology was exclusively studied, it was possible for the error to arise that a merely material mechanism produces remedial effects; but as anatomy first began to yield important results when it was studied comparatively, and psychology is just beginning to afford true enlightenment through a similar procedure, so in physiology only comparative investigation can give genuine insight. But when we have once got on the right track through a clear understanding of relations in the case of the lower animals, it will not be difficult to recognise this view also as the only possible one in the higher stages of organisation.
The reasons for the limitation of the vis medicatrix in the higher animal classes are partly internal, partly external. The inmost and deepest ground is that the organising force turns always more and more away from the outworks, and bends its whole energy to reach the final goal of all organisation, the organ of consciousness, in order to raise this to even higher perfection. The external grounds are that the organs of the higher animal classes are more solid, and also, in consequence of the mode of life of these creatures, are much less liable to fracture and mutilation, but at the most are exposed to wounds and injuries, for the majority of which the healing power of Nature is sufficient; and further, that the greater solidity of structure makes replacement on a large scale physically and chemically difficult. For, on the one hand, we see even in lower animals that aquatic animals, on account of containing a greater quantity of moisture, possess a greater recuperative power than land animals of the same species, e.g., water and earth worms. On the other hand, the chief mass of the animals capable of extensive restoration consists of the same tissues which in man also exhibit the highest recuperative power, e.g., the tissues which mostly give solidity to invertebrate animals (skin, hairs, scales), cellular tissue, vascular system, or even the elementary organic substance of the lowest classes. That, however, these external grounds are not sufficient we see from the Vertebrata, for instance, in their second lowest class, the Amphibia, many of which exhibit a quite wonderful recuperative energy. Spallanzani saw among Salamanders the four legs with their ninety-eight bones, besides the tail with its vertebræ, reproduced six times within three months; in others, the lower jaw, with all its muscles, vessels, and teeth, was regenerated. Blumenbach saw even the eye restored within the space of a year, if the optic nerve remained uninjured, and a part of the coats of the eye remained behind in the orbit. In the case of frogs and tortoises the legs also are sometimes regenerated, but only as long as they are young, and even then but slowly. As the psychical power of the individual is at first active in an exclusively external manner, and then with the advance of age more and more withdraws inwards, and throws itself on the improvement of the conscious life of the mind; so also in all beings the vis medicatrix is the more potent the younger they are, accordingly greatest of all in the case of embryos and all larvæ, which must be regarded as embryos. We cannot, therefore, wonder that the same law obtains in the animal series as a whole, where in the wider sense the lower are related to the higher as embryos or imperfect stages of development.
A very remarkable case is the regeneration of the cerebral hemispheres, observed by Voit in a pigeon which had been deprived of its brain. After five months, the intelligence of the animal having manifestly increased during the latter part of that time, a white mass showed itself in the place of the removed cerebral hemispheres. which possessed altogether the appearance and consistency of the white substance of the brain, and which also passed uninterruptedly and imperceptibly into the peduncles of the cerebrum, which had not been removed. Primitive nerve-fibres with double borders were clearly to be seen, also ganglionic cells.
If we now pass to the Mammalia, and to man in particular, we certainly do not find such striking phenomena as in the lower animals, but always enough to convince us that the dead causality of material processes is insufficient, and that it is a psychical power which, aided by the unconscious representation of the type, and the means requisite for the end of self-preservation, brings about those circumstances in consequence of which the restoration of the normal condition must ensue, according to general physical and chemical laws. In every disturbance this process occurs, unless the power of the unconscious will in mastering its circumstances is too small, so that the disturbance induces a permanent abnormity or death. No medicine can do more than aid that process and facilitate the mastering of the disturbing circumstances, but the positive initiative (the will) must always proceed from the organism itself.
Let us first consider the consolidation of severed tissues and the renovation of a destroyed surface.
The first condition of every new formation (except in the epithelial layers) is inflammation. According to J. Müller, inflammation is “compounded of the phenomena of a local injury, a local tendency to decomposition, and an augmented organic activity which energetically strives to maintain the equilibrium against the tendency to decomposition.” What Müller calls the “local injury,” Virchow calls the pathological stimulus. He says (Spec. Path. u. Ther., i. 72):—“As long as only functional disturbances are observed to follow on an irritation, so long do we speak of irritation; if nutritive disturbances are observable in addition to the functional, we call it inflammation.” He then further calls nutritive disturbance what Müller calls the local tendency to decomposition. Virchow insists quite specially upon the third factor, the effective activity of the inflamed cells. The most striking phenomenon in inflammation is the increased flow of blood to the part where the new formation is to take place, showing itself in redness and increased heat. The law, that the partially increased or diminished blood-pressure accommodates itself to the need of blood in the several organs, is hardly ever to be explained from physical causes alone, since the propulsive action of the heart is uniform in respect of the whole circulation. So far then as the phenomenon is not to be explained by the increased active absorption of the inflamed cells, there must be assumed a direction of the physical circumstances through the willing of the means to accomplish the represented end. (In the normal course of development, an increased congestion takes place at the age of puberty, during pregnancy, and in the abdominal vessels of the bird at the time of brooding; a diminution when the organs cease to be functional, or irreplaceable members have been lost. No less wonderful is the permanently fluid condition of the blood within the blood-vessels, whereas it immediately coagulates on issuing therefrom, even without coming in contact with air.)
In every section of the animal body vessels are cut through; these must first of all be closed, which takes place through the coagulation of the outflowing blood. In the larger trunks an inner and an outer plug is formed, which is easily detached soon after its formation, if the flow of blood is increased by exte
rnal stimulation. In arteries, where the pressure of blood is considerable, the organism is sometimes helped by a swoon. The coagulated mass does not, however, enter into any firm union with the walls, but, like every means of relief employed at an earlier stage of the healing process which has become unnecessary, is subsequently absorbed. After about twelve hours, a pale fluid (plastic lymph) is secreted, which generally immediately afterwards condenses to a membranous opaque neoplasm, which closes up the wound and becomes concrescent with the neighbouring parts. The neoplasm is not mere exuded blood serum, but a secretion from the blood of just as definite a character as any other fluid secretion. It is also no amorphous pulp, but a network of cells thoroughly permeated by copious intercellular fluid, and is formed by proliferation of the connective tissue which has been laid bare by the wound. It forms the matrix for every organic new formation, and blood-vessels, sinews, nerves, bones, skin, all proceed therefrom by gradual change of the cells. “The first step to healing then consists in this: Abundant cells come into existence by means of (?) inflammation, especially in the neighbourhood of the capillary vessels. These are changed by proliferation of their nuclei into cell-cones, and successful artificial injection of the blood-vessels proves that then fine passages without special walls are made between the new-formed cells, into which the injected mass directly penetrates from the capillaries. Accordingly there arises a provisional course for the blood, which presents the appearance of an intercellular net. The same process takes place from the opposite surface of the wound, and thus it happens that through the contact of these paths, several of which expand and become actual vessels, the disturbed circulation is restored to its normal state.” (Dr. Otto Barth in the “Ergänzungsbl.,” vol. vi, p. 630.) In this way, in the first instance only, the plexus of capillary vessels is restored; subsequently, however, also larger blood-vessels are brought again into connection after reabsorption of the plugs. In the Achilles’ tendon of a dog, the regeneration of an excised piece, five lines in length, within four months has been observed, and in nerves from which a piece was excised, a gradual approximation of the two ends, with or without final union. Movement and sensation can in this way be restored without the newly formed mass, even when it exhibits fibrillation, exactly corresponding to tendons and nerves proper, the correspondence being even less close in the case of muscle; but the assimilation of the new formation to the old gradually increases.
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