PERIOD OF DECLINE. 1029 







for food chiefly depends in the Adult; the sole purpose of the Organic or 

 Vegetative operations being (so to speak) to keep the apparatus of Animal 

 life, now fully developed, in working order. The relative activity of the 

 different parts of this apparatus is now somewhat modified. The observing 

 faculties no longer possess the same pre-eminence; the emotional sensibility is 

 less readily excited ; but the intellectual poivers now act, in the modes which 

 have become habitual to them, with a sustained vigor and completeness 

 which they never previously possessed. And so, whilst the muscles are not 

 so easily excited to contraction, and new combinations of movement are 

 acquired with far more difficulty than during the period of growth and de- 

 velopment, the force which they can generate by their contraction is aug- 

 mented, and this force can be kept up for a much longer time in adults than 

 in younger subjects. 



876. The duration of the period over which this " maintenance " may be 

 protracted, without any sensible deterioration, depends in great degree upon 

 the due observance of all the conditions of health. If the various mental 

 and bodily faculties are duly exercised, without being overtasked, if an 

 amount of sleep adequate to their periodic renovation be regularly taken, 

 if a sufficient but not excessive quantity of wholesome food be ingested at 

 appropriate intervals, if the functions by which the blood is prepared, and 

 those by which it is kept in purity, be duly performed, if all such noxious 

 agents as foul air, strong alcoholic liquors, tobacco-smoke, be kept at a dis- 

 tance, and there be no constitutional predisposition to disease on the one 

 hand, nor any exposure to extraneous morbific causes on the other, it may 

 be fairly anticipated that the bodily and mental vigor may be sustained with 

 little deterioration during a long succession of years. The circumstances 

 that most tend to premature decline, are, on the one hand, excessive exertion 

 either of the mental faculties or of the generative power; or, on the other, 

 undue indulgence in food, or in stimulating drinks, or in any practice that 

 tends to disorder the Organic functions, especially by exciting them to undue 

 activity. Every one who, in any of these modes, may " live too fast," 

 is almost certain to pay the penalty in an abbreviation of his term of vigor- 

 ous activity ; which may be either brought to a sudden and final close by 

 fatal disease, or may be prematurely reduced by more gradual decay. And 

 this tendency will of course be more decided, the greater is the amount, and 

 the larger the combination, of those departures from the Laws of Health 

 which give rise to it. 



877. Period of Decline. The decline of life exhibits a much more obvious 

 diminution of the whole vital power of the organism ; for not only is its 

 formative activity now greatly reduced, but its nervo-muscular energy and 

 general vigor progressively diminish, and its generative power becomes en- 

 feebled, or ceases entirely ( 734, 742). Of this diminution in formative 

 power we have evidence in the entire absence of any attempt at new develop- 

 ment, in the less perfect and more tedious manner in which the losses of 

 substance occasioned by disease or injury are recovered from, and in the 

 gradual deterioration of the organism in general. The tissues which are 

 rendered effete by their functional activity, are not any longer replaced in 

 their normal completeness ; for either the quantity of new tissue is inade- 

 quate, so that the bulk of the organs is obviously reduced ; or their quality 

 is rendered imperfect by the production of structures in various phases of 

 degeneration, in place of those which had been previously developed in the 

 fullest completeness. The inferiority of Nervo-muscular energy and of gen- 

 eral vigor are thus evidently the result of the deficiency, and not (as in the 

 period of growth) of the excess, of formative power, and in proportion as 

 the " waste " of the tissues, consequent upon their functional activity, is 



