HUMAN LONGEVITY. 139 



What has just been said about exercises of the body in 

 relation to longevity will, in great measure, apply to the 

 mental functions also. We cannot indeed assume, because 

 facts disprove it, that there is any exact parity between the 

 mind and body in their connection with mere age. The 

 mind may, and often does, retain its faculties little impaired, 

 when vitality, as expressed by the bodily powers, is reduced 

 to the lowest ebb. But let this reduction go further and 

 they too give way ; in obedience to the common law which 

 the Creator has assigned to man on earth. The question 

 before us regards the capacity for prolonging their duration, 

 and the means conducive to this end. And here we come 

 upon the track of a great writer, whose views on the moral 

 and intellectual culture of old age, though somewhat florid 

 in colouring, have always earned the respect due to his name 

 and philosophy. The doctrine of Cicero is that the faculties 

 of the mind in old age are best maintained by their exercise. 

 ' Manent ingenia senibus, modo permaneant studium et 

 industrial In this doctrine, and on the same grounds just 

 asserted as to the preservation of the bodily powers, we may 

 fairly acquiesce. Every intellectual faculty is dulled and 

 diminished by want of use. Each one is maintained in 

 vigour, if not improved, by its fitting and temperate employ- 

 ment. This maxim, true generally to every time of life, re- 

 quires no other modification for old age than the simple one 

 of additional care that there be no habitual excess. Vitality 

 is weakened or exhausted by intemperance of mind as well 

 as of body ; and in old age is less easily repaired. The 

 brain, that organ which comes in such close and mysterious 

 relation to the mental functions, more especially needs this 

 forbearance in advanced life. At this period it readily 

 becomes the subject of disordered action or disease from 

 any excess of use, even of the intellectual powers ; much 

 more still from any intemperance or disorder of the moral 



