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not of itself suffice; this might be done, as any one can test, without swelling out the closed cavity of the mouth. Either there must be a bulging action of the cheeks, through the buccal muscles, or a momentary inspiration, with the nostrils closed, which would bring about the needful disturbance of the atmospheric equilibrium.

We have already alluded to the act of vomiting, as performed through the involuntary fibres of the alimentary canal. More usually and obviously, it takes place through the abdominal muscles. When the pyloric muscular ring (at the outlet of the stomach into the duodenum) contracts tightly, while the cardiac orifice (the entrance to the stomach) is open, the abdominal muscles, operating powerfully, expel the contents of the stomach from the mouth. The action is essentially an irregular one; the due concurrence of all the acts not being provided for by a preconceived arrangement. Sometimes the cardiac fibres are contracted, as well as the pyloric, through the reflex stimulation of the alimentary canal itself; in that case, the attempts at vomiting are ineffectual.

In order to procure the aid of the abdominal muscles, the medulla oblongata must be affected. Hence there is required a sufficiently powerful stimulation of the pneumo-gastric nerves. This may be gained by an irritating contact with the surface of the stomach, the most usual cause of vomiting. The effect may also arise by tickling the fauces, whence must proceed a very powerful stimulation to the medulla oblongata, at the point where the nerves issue to the abdominal muscles. Certain tastes are called nauseous, from their tendency to excite the stomach to vomiting; the nervous agency in this case being the glossopharyngeal nerves, also connected with the medulla oblongata. Nauseous odours probably operate through the same nerves; the olfactory track would carry the influence too far about. Certain sensations, in their origin still more remote from the stomach, bring on sickness; as a severe prostrating blow on the shin, the testicle, or on the eye-ball. The seat of irritation in this case is the brain, in the first instance, from which an influence is diffused to the medulla oblongata. The same may be said of violent emotion generally, which may lead to sickness. Concussion of the These circumstances would indicate the brain is also a cause. result as due to a great loss of cerebral power, and the dis

STIMULANTS OF THE ORGANIC FUNCTIONS.

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turbance of some tonic state or balance, permitting a special and local outflow of stimulus, which the healthy condition holds in restraint. The case of sea-sickness would readily accord with the same view.

The aid given to defæcation by the abdominal and expiratory muscles is probably altogether voluntary. Infants seem incapable of the effort; in them, accordingly, the reflex peristaltic movements of the intestines are the expelling instrumentality.

The expulsion of the male semen is a reflex act operated through the sensory nerves and the cerebro-spinal centres; the muscles are of the voluntary species.

In a Third class of Reflex Actions, the organic functions are affected through the medium of the cerebro-spinal system.

Salivation is controlled by the nerve of taste. A sapid body entering the mouth causes an increased flow of saliva. The salivary glands are all connected with the sympathetic system of nerves; the small arteries of the blood-vessels being kept at a certain point of contraction through the vaso-motor influence of the sympathetic. To produce an increased flow, the muscular fibres are relaxed by influence from the sensory nerves, apparently suspending or diminishing the action of the sympathetic ganglia. The gastric secretion in the stomach is influenced, probably in the same way, through the sensory nerve of the stomach, the pneumogastric. So, the flow of milk in the female breast is augmented by irritating the nipple.

The flow of tears is increased when a foreign body enters the eyelids. The same effect is caused by a strong light; also by irritating the conjunctival, nasal, and lingual branches of the fifth nerve, all which reflect influence on the sympathetic ganglia. When the flow is stimulated by the more remote disturbances of vomiting, violent coughing, laughing, and sobbing, there is probably an intermediate stimulation of the fibres of the fifth pair.

The flow of tears under pain is a relief from the congestion of the brain, and may be forced on by that circumstance, and not by the process last described. The effect of pain is to weaken the cerebral centres, and give more play to the sympathetic, so that the regular consequence is exemplified in the arrest of secretion (as, for example, the saliva and the gastric juice).

The winking of the eye is a reflex act, following the same stimuli as the flow of tears; namely, the presence of a foreign

body, the accumulation of watery drops in the eye, and a strong light. The nerves of the fifth pair are the instrumentality; and the centres of influence are partly the sympathetic, partly the cerebro-spinal (in this instance, probably the medulla oblongata). The complete and energetic closure of the eye, involving not only the eyelids, but also the eyebrows, is altogether voluntary.

The movements of the iris are due to the sympathetic system, controlled by the sensory nerves of the eye-ball, and the motor nerves of the eye. The iris is contracted under a strong light, and expanded as the light becomes feeble. If the process be conducted on the analogy of the foregoing examples, the sympathetic ganglia would control the radial fibres, which keep the eye open; the abatement of this control by sensory action would allow the circular or contracting fibres to operate. It is possible, besides, that the fibres of the third cerebral nerve proceeding to the iris may be stimulated by a reflex influence of the light through some portion of the brain (as the corpora quadrigemina).

In the Fourth, and last, Class of Reflex Actions, muscles, more or less voluntary, are affected through the cerebro-spinal centres. Here we have an approximation to proper voluntary acts; the stimulant in all cases being accompanied with sensation, and the movement being such as the will could execute.

The first case that we shall mention is the contraction of the ciliary muscle, in the adjustment of the eye to near vision. This action, without our consciously willing or wishing it, succeeds to the feeling of indistinctness of the picture when anything is brought nearer to us. Consentaneous with the act, are the narrowing of the pupil and the convergence of the eyes; all the three adjustments co-operating to the distinct vision of near objects. The nerve for regulating the ciliary muscle is supposed to be a branch of the third pair; the contraction of the iris may be due to the same nerve, which likewise governs the convergence of the eyes, through the internal rectus muscle. The nervous centre more immediately concerned is the anterior pair of the corpora quadrigemina, stimulated through the optic nerve.

The muscles of the tympanum are controlled in a manner analogous to the adjusting muscles of the eye. The analogy extends to the mixed supply of nerves; those for the tensor tympani being derived from the sympathetic (like the radial fibres of the iris); those for the stapedius, from the fifth cranial

nerve.

REFLEX MOVEMENTS OF THE SENSES.

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On the theory of the action of these muscles that accords with the above analogy, the tensor tympani tightens both the membrane of the tympanum and the membranes of the foramina of the inner ear, under the influence of the sympathetic ganglia, and renders the ear susceptible, in the highest degree, to sound, like the radial fibres of the iris widening the pupil to the utmost. The feeling of sound in excess would then operate to relax those parts, by the stapedius muscle, which is stimulated through the facial (motor) nerve.

Under the same head we may place the reflex movements of the Senses generally. By these are understood the special movements of the organ itself, as distinct from the more diffused wave of influence accompanying lively sensation. Thus, an object placed in the hand specially stimulates the muscles that bend the fingers, besides producing the more distant effects associated with a sensation as a fact of consciousness. The effect may be seen in any one asleep. A bad smell affects specially the muscles of the nose; a bitter taste brings on wry movements of the mouth.

The word 'Reflex,' as applied to the actions now considered, needs to be specially guarded and explained. It is employed in cases where its obvious meaning is absent, and withheld in others where that meaning is present.*

The notion plainly attached to the word is a circle of influence, wherein there can be distinctly shown an outer or peripheral stimulation, conveyed by incarrying nerves to a ganglionic centre, and bringing on, by way of response, certain movements. The stimulation may be unconscious, as in the intestines, or conscious, as in the adjustment of the eye. The distinction is an important one; it marks out two grades of the effect, a lower and a higher; and distinct names have been employed to express the two-the phrase excito-motor being applied to the first, and sensori-motor to the second.

But it has been very properly remarked, that actions of the highest order of combined volition and intelligence may have

* The term 'automatic' is used as a synonym, or as a substitute, for 'reflex,' but with still less aptness for the purpose. It would serve to indicate the spontaneous activity, and that alone. With proper cautions and explanations, the name 'reflex' is the most suitable that has yet been proposed. 'Involuntary,' although applicable to the class (allowance being made for a margin of transition), is too wide in its meaning.

this reflected character. Any one promptly answering a question, exemplifies a reflex operation, so far as the general meaning is concerned. But such cases are not included among the so-called Reflex actions, these being set in marked contrast to voluntary actions of every kind.

Again, there are included in the class certain effects that are obviously wanting in the peculiarity implied in the name 'reflex.' Thus, we have seen that there are many movements due solely or mainly to central influence, the so-called spontaneous movements; with regard to which, either no peripheral stimulus can be assigned, or the stimulus is insignificant compared with the energy of the response, an energy rising and falling with the physical condition of the central grey masses. The convulsive movements in certain ailments, as hydrophobia, hysteria, chorea, epilepsy, tetanus, &c., must be due to diseased changes in the condition of the nervous centres. These are involuntary movements, but they are not, strictly speaking, reflex. We may give a similar account of yawning; which is probably due to the unequal subsidence of the nervous action, disturbing the balance of the muscular tension. It would be a very forced supposition, to bring it under the literal meaning of reflex action.

In the enumeration of Reflex Actions, there is often included a group of effects distinct from any of the foregoing, namely, those typified by laughter, cries, sobbing, sighing, starting, fidgets, &c. These have been sometimes styled sensori-motor, because they are at the instance of sensations. This circumstance, however, does not show their real characteristic. They are, in my opinion, more aptly brought under emotional diffusion, expression, or embodiment. Every conscious state is accompanied with a diffused wave of effects, muscular and organic, which are stronger according as the feeling is more intense. Pleasing emotions are attended with one class of manifestations,—the smile, for example; states of pain with a different class. The leading emotions of the mind-Wonder, Fear, Love, Anger, &c.-have each a characteristic and well known embodiment or display.

These movements incorporated in our constitution as a portion of the very fact of being conscious (we are often said to be 'moved,' when it is only meant that an impression is made on the mind), may be called 'sensori-motor,' inasmuch as a sensation, when sufficiently powerful, always visibly stimulates them,

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