Part 15 (2/2)

There is a popular prejudice, that the warm bath relaxes people, and that the cold bath braces them; which are mechanical terms belonging to drums and fiddle-strings, but not applicable except metaphorically to animal bodies, and then commonly mean weakness and strength: during the continuance in the bath the patient does not lose weight, unless he goes in after a full meal, but generally weighs heavier as the absorption is greater than the perspiration; but if he suffers himself to sweat on his leaving the bath, he will undoubtedly be weakened by the increased action of the system, and its exhaustion: the same occurs to those who are heated by exercise, or by wine, or spice, but not during their continuance in the warm bath: whence we may conclude, that the warm bath is the most harmless of all those stimuli, which are greater than our natural habits have accustomed us to; and that it particularly counteracts the approach of old age in emaciated people with dry skins.

It may be here observed in favour of bathing, that some fish are believed to continue to a great age, and continually to enlarge in size, as they advance in life; and that long after their state of p.u.b.erty. I have seen perch full of sp.a.w.n, which were less than two inches long; and it is known, that they will grow to six or eight times that size; it is said, that the whales, which have been caught of late years, are much less in size than those, which were caught, when first the whale-fishery was established; as the large ones, which were supposed to have been some hundred years old, are believed to be already destroyed.

All cold-blooded amphibious animals more slowly waste their sensorial power; as they are accustomed to less stimulus from their respiring less oxygen; and their movements in water are slower than those of aerial animals from the greater resistance of the element. There besides seems to be no obstacle to the growth of aquatic animals; as by means of the air-bladder, they can make their specific gravity the same as that of the water in which they swim. And the moisture of the element seems well adapted to counteract the rigidity of their fibres; and as their exertions in locomotion, and the pressure of some parts on others, are so much less than in the bodies of land animals.

2. But as all excessive stimuli exhaust the sensorial power, and render the system less excitable for a time till the quant.i.ty of sensorial power is restored by sleep, or by the diminution or absence of stimulus; which is seen by the weakness of inebriates for a day at least after intoxication. And as the frequent repet.i.tion of this great and unnatural stimulus of fermented liquors produces a permanent debility, or disobedience of the system to the usual and natural kinds and quant.i.ties of stimulus, as occurs in those who have long been addicted to the ingurgitation of fermented liquors.

And as, secondly, the too great deficiency of the quant.i.ty of natural stimuli, as of food, and warmth, or of fresh air, produces also diseases; as is often seen in the children of the poor in large towns, who become scrofulous from want of due nourishment, and from cold, damp, unairy lodgings.

The great and princ.i.p.al means to prevent the approach of old age and death, must consist in the due management of the quant.i.ty of every kind of stimulus, but particularly of that from objects external to the moving organ; which may excite into action too great or too small a quant.i.ty of the sensorial power of irritation, which princ.i.p.ally actuates the vital organs. Whence the use of much wine, or opium, or spice, or of much salt, by their unnatural stimulus induces consequent debility, and shortens life, on the one hand, by the exhaustion of sensorial power; so on the other hand, the want of heat, food, and fresh air, induces debility from defect of stimulus, and a consequent acc.u.mulation of sensorial power, and a general debility of the system.

Whence arise the pains of cold and hunger, and those which are called nervous; and which are the cause of hysteric, epileptic, and perhaps of asthmatic paroxysms, and of the cold fits of fever.

3. Though all excesses of increase and decrease of stimulus should be avoided, yet a certain variation of stimulus seems to prolong the excitability of the system; as during any diminution of the usual quant.i.ty of stimulus, an acc.u.mulation of sensorial power is produced; and in consequence the excitability, which was lessened by the action of habitual stimulus, becomes restored. Thus those, who are uniformly habituated to much artificial heat, as in warm parlours in the winter months, lose their irritability in some degree, and become feeble like hot-house plants; but by frequently going for a time into the cold air, the sensorial power of irritability is acc.u.mulated and they become stronger.

Whence it may be deduced, that the variations of the cold and heat of this climate contribute to strengthen its inhabitants, who are more active and vigorous, and live longer, than those of either much warmer or much colder lat.i.tudes.

This acc.u.mulation of sensorial power from diminution of stimulus any one may observe, who in severe weather may sit by the fire-side till he is chill and uneasy with the sensation of cold; but if he walks into the frosty air for a few minutes, an acc.u.mulation of sensorial power is produced by diminution of the stimulus of heat, and on his returning into the room where he was chill before, his whole skin will now glow with warmth.

Hence it may be concluded, that the variations of the quant.i.ty of stimuli within certain limits contribute to our health; and that those houses which are kept too uniformly warm, are less wholesome than where the inhabitants are occasionally exposed to cold air in pa.s.sing from one room to another.

Nevertheless to those weak habits with pale skins and large pupils of the eyes, whose degree of irritability is less than health requires, as in scrofulous, hysterical, and some consumptive const.i.tutions, a climate warmer than our own may be of service, as a greater stimulus of heat may be wanted to excite their less irritability. And also a more uniform quant.i.ty of heat may be serviceable to consumptive patients than is met with in this country, as the lungs cannot be clothed like the external skin, and are therefore subject to greater extremes of heat and cold in pa.s.sing in winter from a warm room into the frosty air.

4. It should nevertheless be observed, that there is one kind of stimulus, which though it be employed in quant.i.ty beyond its usual state, seems to increase the production of sensorial power beyond the expenditure of it (unless its excess is great indeed) and thence to give permanent strength and energy to the system; I mean that of volition. This appears not only from the temporary strength of angry or insane people, but because insanity even cures some diseases of debility, as I have seen in dropsy, and in some fevers; but it is also observable, that many who have exerted much voluntary effort during their whole lives, have continued active to great age. This however may be conceived to arise from these great exertions being performed princ.i.p.ally by the organs of sense, that is by exciting and comparing ideas; as in those who have invented sciences, or have governed nations, and which did not therefore exhaust the sensorial power of those organs which are necessary to life, but perhaps rather prevented them from being sooner impaired, their sensorial power not having been so frequently exhausted by great activity, for very violent exercise of the body, long continued, forwards old age; as is seen in post-horses that are cruelly treated, and in many of the poor, who with difficulty support their families by incessant labour.

III. _Theory of the Approach of Age._

The critical reader is perhaps by this time become so far interested in this subject as to excuse a more prolix elucidation of it.

In early life the repet.i.tion of animal actions occasions them to be performed with greater facility, whether those repet.i.tions are produced by volition, sensation, or irritation; because they soon become a.s.sociated together, if as much sensorial power is produced between every reiteration of action, as is expended by it.

But if a stimulus be repeated at uniform intervals of time, the action, whether of our muscles or organs of sense, is performed with still greater facility and energy; because the sensorial power of a.s.sociation mentioned above, is combined with the sensorial power of irritation, and forms part of the diurnal chain of animal motions; that is, in common language, the acquired habit a.s.sists the power of the stimulus; see Zoonomia, Vol. I. Sect. XXII. 2. and Sect. XII. 3.

3.

On this circ.u.mstance depends the easy motions of the fingers in performing music, and of the feet and arms in dancing and fencing, and of the hands in the use of tools in mechanic arts, as well as all the vital motions which animate and nourish organic bodies.

On the contrary, many animal motions by perpetual repet.i.tion are performed with less energy; as those who live near a waterfall, or a smith's forge, after a time, cease to hear them. And in those infectious diseases which are attended with fever, as the small-pox and measles, violent motions of the system are excited, which at length cease, and cannot again be produced by application of the same stimulating material; as when those are inoculated for the small-pox, who have before undergone that malady. Hence the repet.i.tion, which occasions animal actions for a time to be performed with greater energy, occasions them at length to become feeble, or to cease entirely.

To explain this difficult problem we must more minutely consider the catenations of animal motions, as described in Zoonomia, Vol. I. Sect.

XVII. The vital motions, as suppose of the heart and arterial system, commence from the irritation occasioned by the stimulus of the blood, and then have this irritation a.s.sisted by the power of a.s.sociation; at the same time an agreeable sensation is produced by the due actions of the fibres, as in the secretions of the glands, which const.i.tutes the pleasure of existence; this agreeable sensation is intermixed between every link of this diurnal chain of actions, and contributes to produce it by what is termed animal causation. But there is also a degree of the power of volition excited in consequence of this vital pleasure, which is also intermixed between the links of the chain of fibrous actions; and thus also contributes to its uniform easy and perpetual production.

The effects of surprise and novelty must now be considered by the patient reader, as they affect the catenations of action; and, I hope, the curiosity of the subject will excuse the prolixity of this account of it. When any violent stimulus breaks the pa.s.sing current or catenation of our ideas, surprise is produced, which is accompanied with pain or pleasure, and consequent volition to examine the object of it, as explained in Zoonomia, Vol. I. Sect. XVIII. 17, and which never affects us in sleep. In our waking hours whenever an idea of imagination occurs, which is incongruous to our former experience, we feel another kind of surprise, and instantly dissever the train of imagination by the power of volition, and compare the incongruous idea with our previous knowledge of nature, and reject it by an act of reasoning, of which we are unconscious, termed in Zoonomia, ”Intuitive a.n.a.logy,” Vol. I Sect. XVII. 7.

The novelty of any idea may be considered as affecting us with another kind of surprise, or incongruity, as it differs from the usual train of our ideas, and forms a new link in this perpetual chain; which, as it thus differs from the ordinary course of nature, we instantly examine by the voluntary efforts of intuitive a.n.a.logy; or by reasoning, which we attend to; and compare it with the usual appearances of nature.

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