The Temple of Nature; or, the Origin of Society: A Poem, with Philosophical Notes

by Erasmus Darwin

4. This disobedience of the fibres of age to their usual stimuli, has generally been ascribed to repetition or habit, as those who live near a large clock, or a mill, or a waterfall, soon cease to attend to the perpetual noise of it in the day, and sleep dining the night undisturbed. Thus all medicines, if repeated too frequently, gradually lose their effect; as wine and opium cease to intoxicate: some disagreeable tastes as tobacco, by frequent repetition cease to be disagreeable; grief and pain gradually diminish and at length cease altogether; and hence life itself becomes tolerable.

This diminished power of contraction of the fibres of the muscles or organs of sense, which constitutes permanent debility or old age, may arise from a deficient secretion of sensorial power in the brain, as well as from the disobedience of the muscles and organs of sense to their usual stimuli; but this less production of sensorial power must depend on the inactivity of the glands, which compose the brain, and are believed to separate it perpetually from the blood; and is thence owing to a similar cause with the inaction of the fibres of the other parts of the system.

It is finally easy to understand how the fibres may cease to act by the usual quantity of stimulus after having been previously exposed to a greater quantity of stimulus, or to one too long continued; because the expenditure of sensorial power has then been greater than its production; but it is not easy to explain why the repetition of fibrous contractions, which during the meridian of life did not expend the sensorial power faster than it was produced; or only in such a degree as was daily restored by rest and sleep, should at length in the advance of life expend too much of it; or otherwise, that less of it should be produced in the brain; or reside in the nerves; lastly that the fibres should become less excitable by the usual quantity of it.

5. But these facts would seem to show, that all parts of the system are not changed as we advance in life, as some have supposed; as in that case it might have preserved for ever its excitability; and it might then perhaps have been easier for nature to have continued her animals and vegetables for ever in their mature state, than perpetually by a complicate apparatus to have produced new ones, and suffer the old ones to perish; for a further account of stimulus and the consequent animal exertion, see Zoonomia, Vol. I. Sect. 12.

II. Means of preventing old age.

The means of preventing the approach of age must therefore consist in preventing the inexcitability of the fibres, or the diminution of the production of sensorial power.

1. As animal motion cannot be performed without the fluid matter of heat, in which all things are immersed, and without a sufficient quantity of moisture to prevent rigidity: nothing seems so well adapted to both these purposes as the use of the warm bath; and especially in those, who become thin or emaciated with age, and who have a hard and dry skin, with hardness of the coat of the arteries; which feels under the finger like a cord; the patient should sit in warm water for half an hour every day, or alternate days, or twice a week; the heat should be about ninety-eight degrees on Fahrenheit's scale, or of such a warmth, as may be most agreeable to his sensation; but on leaving the bath he should always be kept so cool, whether he goes into bed, or continues up, as not sensibly to perspire.

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 puberty. I have seen perch full of spawn, 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.