7 68 THE POPULAR SCIENCE MONTHLY. 



it once was not infrequently stimulates a man to increased exer- 

 tions which may provoke structural changes in the brain, and will 

 certainly accelerate the progress of any that may exist in that or- 

 gan. When a man finds that a great effort is required to accom- 

 plish any mental task that was once easy, he should desist from the 

 attempt, and regulate his work according to his power. With this 

 limitation, it may be taken for granted that the mental faculties 

 will be far better preserved by their exercise than by their disuse. 



Somewhat different advice must be given with regard to bodily 

 exercises in their reference to longevity. Exercise is essential to 

 the preservation of health ; inactivity is a potent cause of wasting 

 and degeneration. The vigor and equality of the circulation, the 

 functions of the skin, and the aeration of the blood, are all pro- 

 moted by muscular activity, which thus keeps up a proper bal- 

 ance and relation between the important organs of the body. In 

 youth, the vigor of the system is often so great that if one organ 

 be sluggish another part will make amends for the deficiency by 

 acting vicariously, and without any consequent damage to itself. 

 In old age, the tasks can not be thus shifted from one organ to 

 another ; the work allotted to each sufficiently taxes its strength, 

 and vicarious action can not be performed without mischief. 

 Hence the importance of maintaining, as far as possible, the equa- 

 ble action of all the bodily organs, so that the share of the vital 

 processes assigned to each shall be properly accomplished. For 

 this reason exercise is an important part of the conduct of life in 

 old age ; but discretion is absolutely necessary. An old man 

 should discover by experience how much exercise he can take 

 without exhausting his powers, and should be careful never to 

 exceed the limit. Old persons are apt to forget that their staying 

 powers are much less than they once were, and that, while a walk 

 of two or three miles may prove easy and pleasurable, the addi- 

 tion of a return journey of similar length will seriously overtax 

 the strength. Above all things, sudden and rapid exertion should 

 be scrupulously avoided by persons of advanced age. The ma- 

 chine which might go on working for years at a gentle pace often 

 breaks down altogether when its movements are suddenly accel- 

 erated. These cautions may appear superfluous, but instances in 

 which their disregard is followed by very serious consequences 

 are by no means infrequent. 



No fixed rule can be laid down as to the kind of exercise most 

 suitable for advanced age. Much must depend upon individual 

 circumstances and peculiarities ; but walking in the open air 

 should always be kept up and practiced daily, except in unfavor- 

 able weather. Walking is a natural form of exercise and sub- 

 serves many important purposes : not a few old people owe the 

 maintenance of their health and vigor to their daily " constitu- 





