62 F. Verzar 



minute volume of respiration are never used to maximal 

 capacity during normal life ; but adaptation produces a margin 

 of safety for all eventualities. 



However, from a certain age on, adaptation as a whole 

 becomes less complete. More and more, a decrease of adapta- 

 tion capacity reveals itself. This is completely different from 

 what happens in earlier life. When the 15-year-old boy shows 

 a decreased accommodation capacity of his eyes, and the near- 

 point of his eyes is no longer 12 but perhaps 20 cm., then 

 something has started which does not increase his adaptation 

 to the variable conditions of life. At the same time, he is 

 already losing the capacity to hear 20,000 Hertz waves. 

 Somewhat later, his athletic powers decrease, being based 

 on the flexibility of his joints as well as on the capacity of 

 his lungs and heart to provide for maximal effort. Nobody 

 will expect the 22-year-old Olympic winner to be in the 

 same condition at the age of 28 or of 30 years. The adap- 

 tation to sight, to hearing, to muscular hyperfunction, has 

 decreased. 



In psychical capacities it is more difficult to see the early 

 start of the decrease in adaptation. It is, however, well known 

 that the training of animals is easier with young individuals. 

 Man does not stop learning, at least if he embarks on a scien- 

 tific career, but he certainly loses the capacity to learn very 

 quickly by heart. Even this fact may have different explana- 

 tions. The limiting factor in the taking-up of new knowledge 

 may be, not the capacity to remember, but rather the 

 accumulated quantity of continuously remembered facts. 

 From the point of view of psychical ageing in humans, as well 

 as in the old leaders of a herd of animals, the factor of experi- 

 ence brings in a rather aberrant evaluation of the old in- 

 dividual. While he is less efficient in the sensory and muscular 

 capacity, he may be increasingly valuable in a certain 

 integrating psychic capacity, owing to his greater accumula- 

 tion of experience in many different situations. 



When the capacity to accommodate visually has reached 

 its end, the human individual has reached his fiftieth year. 



