Related to Invocation of circuits in nineteenth-century discussions of nerves and nervous action.
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'No Physiologist can doubt that the Mechanical force exerted by the Muscles is the expression of certain Chemical changes which take place between their own substance and the oxygenated Blood that circulates through them ; or that the Nerve-force which calls forth those changes, is intimately related to Electricity and other Physical forces. But this Nervous activity has its source in molecular changes in the Nerve-centres; the transmission of Nerve-force along the motor nerve being just as dependent upon Chemical changes taking place between the substance of the Ganglionic centre from which it proceeds and the oxygenated Blood that circulates through it, as is the transmission of an Electric current along the Telegraph-wire upon the Chemical changes taking place between the metals and the exciting liquid of the Galvanic battery. But these changes are themselves capable of being brought about by the various forms of Mental activity just enumerated. Just as a perfectly constructed Galvanic battery is inactive while the circuit is "interrupted," but becomes active the instant that the circuit is "closed," so does a Sensation, an Instinctive tendency, an Emotion, an Idea, or a Volition, which attains an intensity adequate to " close " the circuit, liberate the Nerve-force with which a certain part of the Brain, while in a state of wakeful activity, is always "charged." That Mental antecedents can thus call forth Physical consequents, is just as certain as that Physical antecedents can call forth Mental consequents; and thus the Correlation between Mind-force and Nerve-force is shown to be complete hoth ways, each being able to excite the other.' (14) [1876 ed.]

 

'It has been shown that the development of Nerve-force, whatever may be the mode in which it manifests itself, depends upon a reaction between the Nervous substance (especially its vesicular form) and the circulating Blood... And this Blood has a double function; for, on the one hand, it supplies the material at the expense of which the Nerve-substance is formed, or rather forms itself, by Nutritive action, and so, as it were, lays up a store of potential energy; whilst, on the other, it supplies the Oxygen, by the action of which upon the Nerve-substance (as in the oxidation of the zinc-element of the galvanic battery) this potential energy is converted into actual energy. Of this conversion we have the inost conspicuous example in the production of the Nerve-force which calls forth Muscular movement, and its transmission along the motor nerves; this production and transmission being extremely analogous to that generation of an Electric current, which takes place in a Galvanic apparatus of battery and wires, immediately that the circuit is closed. Now the ordinary state of activity of the Nervous system would seem to correspond closely with that of a moderately-charged Electric battery, which can be discharged by the completion of the circuit; this discharge relieving the tension for the moment, until it is restored by the chemical reaction between the blood and the ganglionic substance. And as there is strong reason to believe that the amount of the Nerve-force generated stands in no less direct a relation than the strength of the Electric current to the activity of that reaction, it is obvious that this, in its turn, will essentially depend on the amount of oxygenated blood which is allowed to pass through the capillaries of the ganglionic substance... an enlargement of the Arterial trunks, and an increase in the quantity of Blood which passes through the Capillaries — constituting the state termed hyperaemia — ecomes the cause of an augmented tension of the Nerve-centres; so that they are much more easily called into action by slight stimuli, and discharge themselves with greater force; whilst the tension may increase to such a degree, that a spontaneous Centric discharge takes place, analogous to that of an overcharged Leyden jar. — Under the guidance of this clue, it seems possible to arrive at a tolerably distinct conception of the nature of the Physical antecedence of every kind of Nervo-muscular action, from the simple Excito-motor up to the Volitional.' (380-381) [1876 ed.]

Related to Material relating to the emergence of physiological aesthetics (c.1850-1910)

Related to Material relating to the history of emotions
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From 1874 edition:

Chapter VII. Of the Emotions

‘Although, as we have seen, there are various forms of Emotional sensibility which are directly called into activity by Sense-perceptions, yet those Emotional states of Mind which directly or indirectly determine a great part of our conduct, belong to the level of the Ideational consciousness; being, in fact, the result of the attachment of the feelings of pleasure and pain, and of other forms of emotional sensibility, to certain classes of ideas. Thus the Cerebrum and the Sensorium would seem jointly concerned in their production; for whilst the Cerebral hemispheres furnish the ideational part of the material, the Sensory ganglia not only give us the consciousness of their result, but invest that result with the peculiar feeling which renders it capable of actively influencing our conduct as a motive power.’ (316)

‘the association of any kind of emotional sensibility of which pleasure and pain afford the simplest type, with any idea, or class of ideas, gives to it an Emotional character; so that emotional states are not by any means limited within the categories under which Psychologists have attempted to range them, – these being, for the most part, generic terms, which comprehend certain groups of ideas bearing more or less similarity to each other, but not by any means including all possible combinations.’ (318)

‘It may also be remarked, in this place, that that the impossibility of classing all the Emotional states of mind under a limited number of categories constitutes a most serious and fundamental objection to any system which professes to mark-out in the Cerebrum distinct seats for the animal propensities, moral feelings, &c.’ (318)

‘By those who regard the Propensities, Moral Feelings, &c., as simple states of mind, it is usually said that their indulgence or exercise is attended with pleasure, and the restraint of them with pain. But, if the view here taken to be correct, is the very co-existence of pleasurable or painful feelings with the idea of a given object, that causes desire or aversion as regards that object; since the mind instinctively pursues what is pleasurable, and avoids what is painful. And thus, according to the readiness with which these different classes of Ideas are excited in different minds (partly depending upon original constitution, and partly upon the habitual direction of the thoughts), and to the respective degrees in which they respectively call-forth the different kinds of Emotional sensibility(as to which there is obviously an inherent difference amongst individuals, analogous to that which exists with regard to the feelings of pleasure or pain excited by external sensations, – sights, sounds, tastes, odours, or contacts), will be the tendency of the mind to entertain them, the frequency with which they will present themselves before the mental view, and the influence they will exert in the determination of our conduct.’ (318-319)

‘All these facts point, therefore, to the conclusion, that whether the elementary states of Emotional sensibility associate themselves with Sensations, with Perceptions, or with Ideas, they are simple modes of consciousness, the organic seat of which must be in the Sensorial centres; and this corresponds well with the character of the purely Emotional movements which, as we have seen, are closely allied to the Sensori-motor in the directness with which they respond to stimuli that excite them.’ (320-321)

‘That the Emotional and Volitional movements differ as to their primal sources, is obvious, not merely from the fact that they are frequently in antagonism with each other, – the Will endeavouring to restrain the Emotional impulse, and either succeeding in doing so, or being vanquished by the superior force of the latter, – but also from the curious fact which Pathological observation has brought to light, that muscles which will still act in obedience to emotional impulses, may be paralysed to volitional, and vice versa.’ (321)

‘The emotions are concerned in Man, however, in many actions, which are in themselves strictly voluntary. Unless they be so strongly excited as to get the better of the Will, they do not operate downwards upon the Automatic centres, but upwards upon the Cerebral; supplying the motives by which the course of thought and of action is habitually determined.’ (322)

'just as the man who commits murder in a state of drunken frenzy is responsible for his irresponsibility, so is the suicide or the murderess, in so far as she has habitually neglected to control the wayward feelings whose strong excitement has impelled her to the commission of her crime. It not unfrequently occurs, moreover, that a delusion of the intellect (constituting what is commonly known as Monomania) has had its source in a disordered state of the feelings, which have represented every occurrence in a wrongful light to the mind of the individual. All such conditions are of extreme interest, when compared with those which are met-with amongst Idiots, and in animals enjoying a much lower degree of intelligence: for the result is much the same in whatever way the balance between the feelings and the rational will (which is so beautifully adjusted in the well-ordered mind of Man) is disturbed; whether by a diminution of the Volitional control, or by an undue exaltation of the Emotions and Passions.’ (323-324)

‘This double mode of action of the Emotions – downwards through the nerve-trunks upon the Muscular apparatus, and also upon many of the Organic functions, – and upwards upon those Cerebral actions which give rise to the higher states of Mental consciousness, – affords a satisfactory explanation of a fact which is practically familiar to most observers of Human nature; namely, that violent excitement of the Feelings most speedily subsides, when these unrestrainedly expend themselves (so to speak) in their natural expressions.’ (324)

'it is well known that the depressing emotions are often worked-off by a fit of crying and sobbing; and the “relief of tears” seems manifestly due to the expenditure of the pent-up nerve-force, in the production of an increased secretion. It is noticed in this case, too, that the absence of any such external manifestations of the depressing emotions, gives them much greater influence upon the course of thought, and upon the bodily state of the individual. Those who really “die of grief”, are not those who are loud and vehement in their lamentations, for their sorrow is commonly transient, however vehement and sincere while it lasts; but there are those who have either designedly repressed any such manifestations, or who have experienced no tendency to their display; and their deep-seated sorrow seems to exert the same kind of anti-vital influence upon Organic functions, that is exercised more violently by “shock”; producing their entire cessation without any structural lesion.’ (p. 326)

‘The influence of Emotional excitement may operate on the Muscles, however, not only in giving-rise to the movements which it directly calls forth, but also in affecting the power of the Will over the muscular system, by intensifying or weakening its action. For there can be no doubt that, under the strong influence of one class of feelings, the Will can effect results such as the individual would scarcely even attempt in his calmer moments; whilst the influence of another class of feelings is exercised in precisely the opposite direction, weakening or even paralysing the force which was previously in full activity.’ (327)

[NB: these notes were initially added to the description of Carpenter's Principles by Asa Jannson]