776 THE POPULAR SCIENCE MONTHLY. 



other of the general and local effects of exercise. It is in the 

 earliest period of mature age that the most characteristic mani- 

 festations of defects of nutrition obesity, gout, and diabetes, in 

 which lack of exercise plays an important part are produced ; 

 and the treatment of them demands imperiously a stirring up of 

 the vital combustion. Placed between a conviction that exercise 

 is necessary, and a fear of the dangers of exercise, the mature 

 man ought, therefore, to proceed with the strictest method in the 

 application of this powerful modifier of nutrition. It is impos- 

 sible, however, to trace methodically a single rule for all men of 

 the same age, for all do not offer the same degree of preservation. 

 We might, perhaps, find a general formula for the age at which 

 the muscles and bones have retained all their power of resistance, 

 and at which the heart and vessels begin to lose some of their 

 capacity to perform their functions. The mature man can safely 

 brave all exercises that bring on muscular fatigue, but he must 

 approach with great care those which provoke shortness of 

 breath. 



The formula is thus subjective in its application, in the sense 

 that it looks rather to the feeling of the person than to the exer- 

 cise itself ; and from this point of view it is exactly applicable to 

 all. One person is taken with shortness of breath at the begin- 

 ning of a fencing bout ; another one of the same age can fence 

 without losing breath, while he tires his legs and arms. Most 

 frequently the question of measure in the practice of exercise is 

 more important than the choice of the kind. Some exercises are 

 dangerous only on account of the temptation they offer to impet- 

 uous temperaments to pass beyond reasonable bounds. Thus 

 fencing, which prematurely wears out too enthusiastic swords- 

 men, may remain a very hygienic exercise for the man of fifty 

 years, provided he is enough master of himself to moderate his 

 motions. There are exercises, however, which of themselves im- 

 ply the necessity of a violent effort or a rapid succession of move- 

 ments ; among these are some of the exercises with gymnastic ap- 

 paratus, wrestling, and running. These should be absolutely pro- 

 hibited to the elderly man. This rule can not be invalidated by 

 the rare examples of men who have been addicted to such exer- 

 cises till an advanced age. Such men have continued, in respect 

 to their structure, younger than their age ; they have kept their 

 elastic arteries as other persons keep their black hair. They are 

 physiological exceptions, and general formulas do not regard 

 exceptions. 



The need which the elderly man feels of a stimulation of his 

 organic combustion may be satisfied in other ways than by exer- 

 cises of strength and agility. It is, in fact, the sum of work that 

 regulates the quantity of heat expended by the human body, and 



