ether modes of sympathetic connection, without the immediate concurrence of nerves, are pointed out by physiologists : as by blood vessels, in the sympathies of the uterus and breasts; from the anastor rnoses of the epigastric and internal mam mary arteries ; by lymphatics ; by analo, gy of the respective functions, as the sympathy of the lungs and common inte gument,.
Habit, or the reiterated repetition of certain acts or motions, has a powerful in fluence in the animal economy. But it operates much more decidedly on the animal, or exterior, than on the organic, or interior life. It has the effect of di minishing the sensibility of our organs, as appears from the effect of using pes saries in the vagina, catheters in the ure thra, &c. Relative pleasure or pain am brought by the influence of this principle to the state of indifference. Things are agreeable or disagreeable, by a compari between the impression they make on the senses and the state of mind re ceiving that impression. Hence the im pressions produced on our organs in the cases just mentioned, although at first - painful, are soon disregarded. Pleasant sensations are the same. The cook and the perfumer are not alive to the enjoy ments which they procure for others. The pleasing emotions connected with the sight and hearing are soon rendered obtuse by repetition ; and any pleasure constantly repeated produces the same series of feelings ; vie. pleasure, indiffe rence, satiety, and .even aversion. The mind is the centre of these changes. It institutes a comparison between the ac tual sensation and the preceding impres sions, and in proportion to the difference between these will be the vivacity of the present impression. It belongs, there fore, to the nature of pleasure and pain to destroy themselves, and to cease to ex ist because they have existed. The art of prolonging the duration of our en joyments consists in varying their sour ces.
Habit, however, which deadens sensa tion, augments and brings to perfection the judgment.
Most of the functions of the organic life are removed from the dominion of habit ; viz. circulation, respiration, &c. ; yet the influence of this principle is unquestionable in some parts of the or ganic functions, as the urinary secretion, evacuation of feces, hunger and thirst, &c.
Voluntary Motions and Muscular Action.
Having already gone over the subject of sensation, one of the offices of the nerves, the other, motion, remains for consideration. The motions of the body
have been commonly divided into two classes, the voluntary and involuntary. The action of the heart, stomach, and in testines, &c. exemplifies the latter ; while the former are the actions of almost all the other muscles of the body. Some are of a doubtful nature, as those of re spiration, of the ossicula auditus, and the cremasters. Different physiologists as sign these to one of the above classes, or to a mixed division.
The arrangement is not unexceptiona ble. There are few functions entirely free from the operation of the will, if we consider the Connection of the imagina tion and passions of the mind with that power : as, on the contrary, many muscu lar motions, which were originally arbi trary, become by the force of habit quite involuntary. Thus we can hardly bend the little finger without the ring fin ger; and cannot help winking, if a per son brings his finger rapidly towards our eye, although we are certain that he will not strike us. Again, mus cles which usually obey the will, refuse obedience under circumstances; hence the difficulty of describing a circle with the hand and foot of the same side in op posite directions, of moving the two hands with an opposite circular motion, &c. Numerous instances might be quot ed of the power of the will over motions that are usually involuntary ; we shall merely mention the fact, supported by the personal testimonies of Drs. Barnard and Cheyne, of an English officer who could influence the action of his heart and arteries (" Treat. on Nervous Dis eases," p. 307.) Perhaps these pheno mena may be accounted for by a reaction of the sensorium, excited by a mental stimulus.
We may observe of the voluntary mo tions in general, that they form the chief character that distinguishes the animal and vegetable kingdoms. No plant has yet been discovered that seeks its food by voluntary motion ; nor, onthe contra ry, is any animal known, that does not either possess a power of locomotion, or at least procure its food by the volun tary motion of some organ or member. These motions in our own bodies spew the very complete harmony between the mind and the material fabric, as we shall readily admit, when we observe the won derful celerity with which the fingers of the violin player, or the organs of speech of a person speaking, move, and recol lect that an act of volition is necessary for each motion.