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Show .. ~6 Additional Notes. well as from the disobedience of the muscles and org_ans of sense to t h e1· r usua 1 s t'1m ul1' ,• but this less 1noduction of sensonal powe. r must . depeml on the inactivity .of the glands, which compose. the bJ~aJr~, and arc believ~cl to separate 1t perpetu.ally fl'om the blpod: and JS 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 previo~sly exposed to a greater quantity of stimulus, or to one too long contmuc~l; because the expenditure of sensorial power has then been greater than 1t 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 su~h a degree as was daily I"estored 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 procluced new ones, and suffer the old ones to perish; for a further account of stimulus and the conse· quent animal exertion, see Zoonomia, Vol. I. Sect. ] 2. II. Means oJpreventing old age. The ineans of preventing the approach of age must thel'efore consist in preventing the ine:xcitability of the fibres, or the diminution of the production of sensorial power. I. 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 1·igidity: nothing seems so well adapted to both these purpo.sc' as the use of the warm bath; and esp~cially in Old Age and Deat lt. 27 those, who become thin or emaciated with ao·c ., d h 1 1 • • < o , <•n w o 1ave a tard and dry skm, wtth hardness of the coat of th ·t · h' 1 . e at enes; w rc 1 feel under the fing er ldce a cord · the patient sh ld 't · ' ou Sl 111 warm water for half an hour every day, or alternate days, or t'vice a week. the heat should be about llinety-eight degrees 011 Fahrenheit's scale ~r of such a warmth, as may uc mo t aoTeeablc to }11·s s t' b' . ' o ensa ron; ut on ~eavmg the bath _he should always be kept so cool, whether he goe mto bed, ~r contmuc up, as not sensibly to perspire. There IS a popular prejudice, that the warm hath relaxes people, and ~hat the cold bath brace them; which are mechanical terms he- . lon~~~g to drui~& and :fic~dle-strings, but not applicable except metaphoucaliy to ~n1mal bodtes, and then commonly mean weakness and str~ngth: durmg the continuance in the bath the patient does not lose Weight, unless he goes in after a full meal, but o·enerally wei()'hs heavier h b . . b b a~ t e a sorptwn 1s greater than the perspiration; but if he suffers h1mselfto sweat on his leaving the bath, he will undoubtedly ue weakened by the inc1·vased action of the system, and its exhaustion: the sa~e occurs to t.hose who are heated by exercise, or by wine, or sp1ce, but not dunng 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 iu size, a~ 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 whalefishery 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 |