BIOLOGY IN ITS WIDER ASPECTS 1267 



seem to be immortal; the Amoeba never dies a natural death; and 

 perhaps there are some very simple many-celled animals which never 

 grow old; but all the higher animals age. Why should this be? The 

 answer given by the most profound student of the subject, namely, 

 Prof. Child of Chicago, is that what happens is a slow accumulation 

 of unrecuperated arrears of wear and tear, effects of fatigue, which 

 are not made completely good by food, rest or sleep. All through 

 life there is a contest going on between the processes of rejuvenes- 

 cence and senescence, and for a long time rejuvenescence is well 

 ahead. With plenty of food, rest and sleep, rejuvenescence has its 

 innings. But slowly the tortoise creeps up on the hare and senescence 

 begins to gain on rejuvenescence. Inside the cells, especially in what 

 one might call crudely the framework, there are fatigue effects 

 which are not made good, especially in the hard-worked organs, 

 such as the liver, kidneys, heart and brain, to put them in their 

 proper order, for the brain relatively seldom suffers from over- 

 work. In all these hard-working organs the colloidal intra-cellular 

 films, which separate the living matter into areas, undergo wear and 

 tear which is not perfectly recuperated. In other words, it is not the 

 living matter which gets fatigued ; the furnishings of the laboratory 

 are worn out. It is probable that ageing is due to the accumulation 

 of unrecuperated wear and tear in the colloidal framework of tissues 

 and cells. Of course many men do not age at all, but their life ends in 

 various ways which are just worth recalling. A man may die before 

 ageing through an accident; or because of some virulent microbe; 

 or he may die from some malignant growth which still largely 

 remains a mystery; or he may die from over-eating, over-drinking, 

 or over-anxiety — all producing toxic effects which end in death; 

 or it is possible that he may die from some badly deteriorating 

 environment or occupation. Relatively rarely does he die from over- 

 work, though this is common among bees. 



But suppose man weathers all crises and passes into senescence, 

 what in the name of Biology can we say to him then ? Usually it is 

 too late: but, especially if he has been biologically trained, he may 

 have anticipated to some extent this senescent period. We use the 

 word "senescence" for what is normal, and "senility" for that kind of 

 ageing in which disintegrative processes have begun to occur in the 

 body. The advice from the biologist's point of view would be to 

 avoid bad debts due to bad habits. Senescence is more likely to be 

 pleasant when the man has avoided certain kinds of arrears. Secondly, 

 that he should cultivate hobbies and interests for this ageing period ; 

 for example, he might then begin to play golf or to geologise, and thus 

 have a new interest for the senescent period. Moreover, he should 

 cultivate positive rejuvenescence, if he can discover the line that is 

 suitable for him. He should join the Order of the Old and Bold and 

 find in the evening of life a joyous time. 



