Nerve energy

“ In the most complex case, that of man, there are a number of nerve-endings, or small lumps of protoplasm, embedded in the tissues all over the body, or highly specialised and grouped together in separate organs such as the eye and ear, from which a nerve-fibre leads direct to the brain, or to the spinal cord and so up to the brain. These nerve-endings receive the different vibrations by which outward energy presents itself, which propagate a current or succession of vibrations of nerve-energy along the nerve-fibre. ”

“ The incoming nerve-fibres serve to conduct stimuli or impressions to the cells in the nerve-centre; and, when the cells thus receive a stimulus or impression, they liberate a discharge of nervous energy, which then courses down the outgoing nerve-fibres to be distributed either to other nerve-centres or else to muscles. It is in this way that nerve-centres are able to act in harmony with one another, and so to coördinate the action of the muscles over which they preside. This fundamental principle of neurosis is what physiologists call the principle of reflex action ”

“ A doubt must always remain, whether nerve has not been present; and from this doubt will arise another still more difficult to solve, whether the influence produced or excited by the metals have passed through the nerve to the muscles? or if it have merely acted as a stimulus to the nerve, serving to rouse that unknown energy, by which nerves are known in certain circumstances to excite muscles to contraction. ”

“ The vital activity of this whole arrangement of nerve fibres, including sensory and motor in one system, depends upon living connection of all with the great nerve centre in the brain, where the nerve energy is provided which keeps all in functional activity. Only, there is this striking difference with the two sets of fibres, that in the case of the sensory nerve the pulsation of energy is upwards to the brain, in the case of the motor nerve it is downwards towards the muscle. ”

“ According to the opinion of the physicists we know external events directly by means of the organs, the nerves of which serve passively to support consciousness in the perception of such events. On the contrary, according to the opinion of most physiologists, the nerve fibers are active in the apprehension of external events, they modify it, alter it until it is well nigh unrecognizable, and turn it over to consciousness only after the original process has undergone still another transformation{193} into new forms of mechanical energy in the ganglion cells of the outer brain. ”

“ Stored energy is like that of coal in the bin; dammed-up energy is like that of steam in the boiler.
Dammed-up energy in the nerve centers accounts for the persistence of a tendency to reaction after the stimulus has ceased. It accounts for the "delayed reaction" and similar cases. But how shall we account for preparatory reactions? We have a nerve center in an active state, tending to discharge into a certain lower motor center, but unable to do so because a peripheral stimulus is necessary, in addition, in order to arouse this lower center. ”

“ Thus the total energy of the nerve cell or the neuron may be divided into normal dynamic energy, reserve energy, static energy, and organic or necrotic energy. The various nervous and mental diseases may thus be correlated with the flow and ebb of neuron energy, with the physiological and pathological processes that take place in the neuron in the course of its activity and reactions to the stimuli of the external and internal environment. ”

“ The function of nerve-cells is different, viz. that of accumulating nervous energy, and, at fitting times, of discharging this energy into the attached nerve-fibres. The nervous energy, when thus discharged, acts as a stimulus to the nerve-fibre; so that if a muscle is attached to the end of a fibre, it contracts on receiving 25 this stimulus. I may add that when nerve-cells are collected into ganglia, they often appear to discharge their energy spontaneously; so that in all but the very lowest animals, whenever we see apparently spontaneous action, we infer that ganglia are probably present. ”

“ The nerve fibers, on the other hand, are conductors of nervous energy. They furnish a pathway along which the nerve energy generated by the cells may travel. Made up as they are of living nerve substance, the fibers can also generate energy, yet it is their special function to conduct influences to and from the cells. ”

“ Ingoing and outgoing nerve currents with their various end reactions may be modified by the nerve centers. Nerve currents' may be intensified, decreased in energy, or even entirely inhibited by central ganglia or by their mutual interaction and interferences. ”

“ The Nervous Energy is stopped by a tight Ligature or by the transverse Incision of a Nerve, although its divided Parts are thereafter placed in contact with each other; whereas the Electrical Fluid or the Fluid excited by the Metals, passes readily, downwards or upwards, along a Nerve which has been tied or cut.
6. After the Limb of a living Animal has been amputated, frequent Convulsions of the same Muscles may be excited by applying Mechanical or Chemical Stimuli to its Nerves ”

“ But, when we have got to nerve element and nerve force, it behooves us not to rest content with the general idea, but to trace, with attentive discrimination, through the nervous system the different kinds of nervous cells, and their different manifestations of energy. ”

“ It is entirely credible that a nervous impulse coming inwards along a sensory fibre should have a side-effect in the shape of a sensation; but why the physical energy embodied in the nerve-impulse should on that account be debarred from producing all the physical effects which it would have produced had there been no sensation, and why these in turn should not go on to produce all their natural effects in conformity with the laws of physics, it is difficult to understand. ”

“ So information obtained from various other sources points toward the conclusion that in all activity energy stored in nerve cells is dissipated.
Recent experimental studies have given us reasons for believing that nerve cells in different individuals yield up their energy in response to stimulation with varying degrees of readiness. ”

“ In experiments, the animal sensibility of the nerve seems to be gradually exhausted, and finally ceases. I convinced myself of this upon the eighth pair of nerves, in making my experiments upon the injection of black blood into the brain. At the moment the nerve is raised and drawn to detach it from the carotid with which it is connected, the animal cries out and is much agitated; but after the same thing is repeated two or three times, he208 no longer gives any signs of pain. If we cease to excite the nerve for an hour or two, the sensibility returns with great energy, when it is drawn again. ”

“ The speciality of nerve-tissue is its pre-eminence in directive energy. Like all other tissues, it grows, develops, and dies; but above all others it has what we call excitability, or readiness in discharging its energy in a directed stream. By its topographical distribution it plays the functional part of exciting the activity of other tissues: it transmits molecular disturbance from periphery to centre, from centre to centre, and from centre to muscles, vessels, and glands. When a muscle is313 excited it moves, and when a gland is excited it secretes ”

“ To reveal them, the careful analysis of the physiologists is required. They are acts, in most cases silent and invisible, which we should scarcely recognize but by their effects, after they have terminated in familiar, phenomenal forms. This is, for example, what goes on in the muscle in process of shortening, in the nerve carrying the nervous influx, in the secreting gland. And this is what constitutes the different forms of energy which we call vital properties. M. Chauveau and M. Laulanié use the phrase physiological work to distinguish them. Vital energy would be preferable. ”

“ However great the mystery of the relation of body to mind, it is quite true that the nervous system is the mechanism by and through which all sensation comes, and that in our experience in the absence of nerves there is neither sensation nor consciousness. The nerves themselves are but complex chemical structures; their molecular constitution is said to embrace as many as 20,000 atoms, chiefly carbon, hydrogen, oxygen, and nitrogen. There must be continuity of this structure too, for to sever a nerve is to paralyze all beyond. ”

“ And it is this readiness of organic tissues to respond to a suitable stimulus that physiologists designate by the term "excitability."
Nerves, no less than muscles, present the property of being excitable. If, together with the excised muscle, there had been removed from the animal's body an attached nerve, every time any part of this nerve is stimulated the attached muscle will contract as before. ”

“ On all sides the idea of nerves deriving their power from another source than their own substance is seen to be untenable. A priori this might have been concluded. Neurility is the vital property of nerve-tissue. “Nerve-force” is nerve-action—molecular changes in the nerve itself, not in some remote substance. That nerve and centre are vitally connected is true; and what their physiological relations are will hereafter be examined; but we must dismiss the idea of nerves having the relation to centres that electrodes have to batteries. ”

“ By the separation of a main branch of one of the nerves of sensation, although all the operations of life will still proceed, the organ to which that nerve goes is dead to its particular sense. In like manner, if one of the nerves of volition is divided, the member will not obey the inclination of the brain. It is evident, therefore, although many of the great phenomena of vital force are dependent on the nervous system, and the paralysis of a member ensues upon the separation or the disease of a nerve, that the nerves are but the channels through which certain influences are carried. ”

“ A stimulus applied to a nerveless muscle can only course through the muscle by giving rise to a visible wave of contraction, which spreads in all directions from the seat of disturbance as from a centre. A nerve, on the other hand, conducts the stimulus without sensibly moving or undergoing any change of shape. Now, in order not to forget this distinction, I shall always speak of muscle-fibres as conveying a visible wave of contraction, and of nerve-fibres as conveying an invisible, or molecular, wave of stimulation. ”

“ Continuing his experiments, he proved that there is a nervous circle connecting the muscles with the brain, that one nerve is not capable of transmitting what is called the nervous spirits in two different directions at one instant of time, but that for the regulation of muscular action there is a nerve of sensibility, to convey a sensation of the condition of the muscles to the sensorium, as well as a nerve of motion for conveying the mandate of the will to the muscles. ”

“ When a stimulus of any kind, whether mechanical, chemical, electrical, or vital, acts upon the living nervous substance, it produces an impression on that nerve substance and excites within it some particular change, and the property by which this takes place in the nerve substance has been called its excitability or neurility. ”

“ In other words, the supply of nerve-force being ample, the cells will energize pleasantly: when the nerve-force is insufficiently produced, or by action is exhausted, the energizing will be attended with proportionate pain. ”

“ Nerve Stimuli.—While the properties of irritability and conductivity supply a necessary cause for the production and transmission of nervous impulses, these alone are not sufficient to account for their origin. An additional cause is necessary—a force not found in the nerve protoplasm, but one which, by its action on the protoplasm, makes it produce the impulse. In this respect, the neuron does not differ essentially from the cell of a muscle. Just as the muscle cell requires a stimulus to make it contract, so does the neuron require a stimulus to start the impulse. ”

“ And our evidence that nerve-force is thus originated, consists not only of such facts as the above, but also of more conclusive facts established by direct experiments on nerves—experiments which show that nerve-force results when the cut end of a nerve is either mechanically irritated, or acted on by some chemical agent, or subject to the galvanic current—experiments which prove that nerve-force is generated by whatever disturbs the molecular equilibrium of nerve-substance. ”

“ At the surface of the body and limbs, the external termini of the nerves are exposed to disturbance by contact with an external object. Along the highly sensitive and minute conductor, the nerve which has by contact with an external object at its outer extremity received a slight shock, there passes through the fluid or semi-fluid substance of the nerve a wave of disturbance, or a succession of such waves. This disturbance reaches the brain, the great nerve-center, where it becomes a feeling. ”

“ All the operations of the nervous system are performed by the influence of the nervous fluid, which is generated in the gray portions of the brain and ganglia. Whenever a nerve is cut off from its connection with these nervous centres, its power is gone, and the part to which it ministered becomes lifeless and incapable of motion. ”

“ During stimulation, therefore, a nerve exhibits a negative variation. We may express this in a different way by saying that a ‘current of action’ was produced in response to stimulus, and acted in an opposite direction to the current of injury (fig. 2, b) . The action current in the nerve is from the relatively more excited to the relatively less excited. ”