49° POPULAR SCIENCE MONTHLY 



Pasteur Institute in Paris, some of whose publications many of you 

 have doubtless read, that his conception of the nature of senility, of 

 old age, could best be expressed in a single word, atrophy. " On resume 

 la senilite par un seul mot : atrophic" 5 That is his estimate of old 

 age. But that is not the only estimate of old age which has been made 

 up to the present time. We find one, which is much more prevalent, 

 is that which connects it with the condition of the arteries. Indeed, 

 Professor Osier has written this sentence — " Longevity is a vascular 

 question, and has been well expressed in the axiom that a man is only 

 as old as his arteries." Now these are medical views, not biological, 

 and you will find that there is a very extensive literature dealing 

 with old age in man based upon the conception that old age is a kind 

 of disease, a chronic disease, an incurable disease. Medical writers 

 have put forward various conceptions giving a medical interpretation 

 of this disease. That to which I just referred is the favorite one, the 

 one you are most likely to hear from physicians to-day — namely, the 

 theory of arterial sclerosis, that the hardening of the walls of the 

 arteries is the primary thing; it interferes with the circulation, the 

 bad circulation interferes with the proper working of every part of the 

 body, and as the circulation becomes impeded, various accessory results 

 are produced in the body in consequence. It is brought to a lower 

 or more diseased condition than before. And so they interpret sclerosis 

 of the arteries as the primary thing, because they can trace so many 

 alterations in the old which resemble diseased alterations, to these 

 natural changes in the arteries by which they acquire hardened and 

 inelastic walls, which prevent the proper response of the artery to 

 the heart beat, upon which the normal healthy circulation largely 

 depends. Another interpretation, very curious and interesting, is that 

 which has been recently offered by the same Professor Metchnikoff 

 whom I have just mentioned. He has written a book upon the ' Nature 

 of Man,' translated in 1903, and published in this country. It is an 

 interesting book. It gives a most attractive picture, incidentally, of 

 Metchnikoff himself, a man of pleasantly optimistic temperament, but 

 a man thoroughly imbued with the spirit which has so often been 

 attributed to contemporary scientific men, of cold, intellectual regard 

 towards everything, towards life, towards man, towards mystery. For 

 him mysteries of all sorts have little interest. Those things which 

 are mysterious are beyond the sphere of what can hold his attention. 

 He must reside in the clear atmosphere of definite, positive fact. This 

 mental bias is shown in his book. He reviews in a happy way various 

 past systems of philosophy; he describes various religions; and he 

 points out his reasons for thinking that all of these are insufficient, 

 that there is no satisfaction to be derived from any of the ancient 



5 L 'Annie biologique, Tome III... p. 256, 1897. 



