THE CONSERVATION OF ENERGY. 407 



begin to make themselves felt, is shortness of breath on exertion. This 

 has to do more with faults in the action of the circulation and the vaso- 

 motor nerves than in the lungs. The old man finds himself distressed 

 in his breathing while undergoing a degree of exertion which aforetime 

 would produce no noticeable effects. The heart muscle is old, relaxed 

 and softened and contracts imperfectly and readily shows exhaustion. 

 This need not produce alarm, but if the condition rapidly increases 

 it may be significant of some important change and should be referred 

 to the medical adviser. In fact, it can not be repeated too often that 

 the more constantly the aged person remains under observation of a 

 wise physician, the more safely can it be promised that he will live 

 happily and long. There is a symptom which is most terrifying and 

 frequently occurs in the aged, and that is a sudden agonizing chest 

 pain, during which the sufferer, unless he be of unusual mental equi- 

 poise, feels that he shall instantly die. This may come on suddenly 

 without previous warning and requires the best medical advice, but it 

 almost always passes and may recur many times and is capable of much 

 relief. It may be a symptom of chronic myocardial degeneration. 



The lungs also, in most instances, share in the process of death. 

 The changes which occur in the aged lung are degenerative and 

 need have nothing to do with any previously disordered processes in 

 them. Again it may happen that certain changes common in old age 

 take place and prove to be most distressing; the chief of these are 

 asthma, chronic pneumonia and bronchitis. Pneumonia in the aged is a 

 very serious affection, and it is stated that the largest number of deaths 

 in old people are caused, or accompanied by, acute broncho-pneumonia. 



The digestive organs sometimes give away while the rest of the or- 

 ganism remains in fairly good condition. Sir William Thomson has 

 written most charmingly upon the digestive disorders of elderly folk, 

 and it would be well for every old person to read his suggestive essays. 

 Unless care is observed in regulating the diet (and the chief point here 

 is rather a reduction in the amount than particularizing as to the items 

 of food taken), distressing phenomena will constantly arise. Fortu- 

 nately this is easily avoided, although not so readily cured. Sir 

 William Thomson makes the assertion that the disappearance of the 

 teeth is a plain indication of the return to a second childhood, and there- 

 fore the food should be of such a character as may not require the 

 assistance of the teeth in mastication. He advises most wisely, although 

 his recommendation can not be taken literally, that the teeth be 

 not replaced by artificial ones, for thereby is a peril lest more food be 

 taken than the organism can dispose of. The fact that the various 

 organs concerned in the elaboration of food share very early in the 

 degenerative changes of age makes it clear that the character of the 

 food taken should be so simple in kind that no great strain would be 



