760 THE POPULAR SCIENCE MONTHLY. 



era origin. New facts connected with longevity have, moreover, 

 been collected within the last few years, and some of these I pro- 

 pose to examine, and further to inquire whether they teach us 

 any fresh means whereby life may be maintained and prolonged. 



But, before entering upon the immediate subject, there are 

 several preliminary questions which demand a brief examination, 

 and the first that suggests itself is, What is the natural duration 

 of human life ? This oft-repeated question has received many dif- 

 ferent answers ; and inquiry has been stimulated by skepticism as 

 to their truth. The late Sir George Cornewall Lewis expressed the 

 opinion that one hundred years must be regarded as a limit which 

 very few, if indeed any, human beings succeed in reaching, and 

 he supported this view by several cogent reasons. He pointed 

 out that almost all the alleged instances of abnormal longevity 

 occurred among the humbler classes, and that it was difficult, if 

 not impossible, to obtain any exact information as to the date of 

 birth and to identify the individuals with any written statements 

 that might be forthcoming. He laid particular stress upon the 

 fact that similar instances were altogether absent among the 

 higher classes, with regard to whom trustworthy documentary 

 evidence was almost always obtainable. He thought that the 

 higher the rank the more favorable would the conditions be for 

 the attainment of a long life. In this latter supposition, however, 

 Sir George Lewis was probably mistaken : the comforts and lux- 

 uries appertaining to wealth and high social rank are too often 

 counterbalanced by cares and anxieties, and by modes of living 

 inconsistent with the maintenance of health, and therefore with 

 the prolongation of life. In the introduction to his work on 

 " Human Longevity," Easton says, " It is not the rich or great . . . 

 that become old, but such as use much exercise, are exposed to 

 the fresh air, and whose food is plain and moderate — as farmers, 

 gardeners, fishermen, laborers, soldiers, and such men as perhaps 

 never employed their thoughts on the means used to promote 

 longevity." 



The French naturalist, Buffon, believed that, if accidental 

 causes could be excluded, the normal duration of human life 

 would be between ninety and one hundred years, and he sug- 

 gested that it might be measured (in animals as well as in man) 

 by the period of growth, to which it stood in a certain proportion. 

 He imagined that every animal might live for six or seven times 

 as many years as were requisite for the completion of its growth. 

 But this calculation is not in harmony with facts, so far, at least, 

 as man is concerned. His period of growth can not be estimated 

 at less than twenty years ; and if we take the lower of the two 

 multipliers, we get a number which, in the light of modern evi- 

 dence, can not be accepted as attainable. If the period of growth 



