AGE, GROWTH AXD DEATH 485 



thereby rather lost than gained ground. Indeed in the skeleton this 

 principle of loss is already revealing itself. In the interior of the 

 bones of the arms, of the legs, we find a spongy structure, bits of bone 

 bound together in many different directions, as are the spicules or 

 fibers in a sponge, and by being bound so together they unite lightness 

 with strength. As you know a column of metal, if hollow, is stronger 

 than the same amount of metal in the form of a rod. So with the 

 bones. If they have this spongy structure, if their interiors are full 

 of little cavities with intervening spicules acting as braces in every 

 direction, then they acquire great strength with little material. Xow 

 in the old the internal spongy structure is dissolved away and there is 

 left only a hard external shell. Partly on this condition depends the 

 greater liability of the bones in the old person to break. If we ex- 

 amine the muscles we see that they have become less in volume, and 

 when we apply the microscope to them we see that the single fibers on 

 which the strength of the muscles depends have become smaller in 

 size and fewer in number. 2 The muscle has actually lost; it is in- 

 ferior, physiologically speaking, to what it was before. You remember 

 how melancholy Jacques reminded us of this fact in speaking of the 

 hose ' a world too wide for his shrunk shank.' His saying is justified 

 by the loss of the muscles in volume and strength. The same phe- 

 nomenon of atrophy shows itself in the digestive organs. Those 

 minute structures in the wall of the stomach by which the digestive 

 juice is produced, undergo a partial atrophy, in consequence of which 

 they are less able to act; they are not so well organized, therefore, not 

 so efficient as in earlier stages. The lungs become stiffened; the 

 walls which divide off an air cavity from the neighboring air cavities 

 do not remain so thin as in youth, but become thickened and hardened, 



J 7 7 



and the vital capacity of the lungs, that is to say the capacity of the 

 lungs to take in and hold air, is by so much lessened. The heart — 

 it seems curious at first — is in the old always enlarged; but this does 

 not represent a gain in real power. On the contrary, if we study 

 carefully the condition of the circulation of the blood in the old, we 

 find that the walls of the large blood-vessels, which carry the blood 

 from the heart and distribute it over all parts of the body — vessels 

 which we call arteries — have lost the elastic quality which is proper 

 to them and by which they respond favorably to the pumping action 

 of the heart. Instead they have become hard and stiff. "We call this 

 by a Greek term for hardening, sclerosis, and arterial sclerosis is one 

 of the most marked and striking characteristics of old persons. JSTow 

 when the arteries become thus stiffened, it requires a greater force 



2 This statement is the one currently accepted — but I have found, as yet, no 

 exact investigation upon the relative size and number of the muscle fibers in old 

 persons. 



