HORSE-BACK RIDING. 105 



est ages to decide the duration and natural limits of 

 human life. Among modern theories, we have first 

 that of Schubert, which has for its basis the revo- 

 lution of the earth. He maintains that the human 

 life ought to be 70^ years, because it should have 

 as many days as the precession of the equinoxes 

 (founded on a particular movement of the axis of the 

 earth) includes years — that is to say, 25,920. 



Buffon, supported by a physiological idea, has estab- 

 lished as a principle that the entire duration of life 

 can be measured in some manner by that of the time 

 of its growth. But this great naturalist missed an 

 essential point in the solution of this problem : he 

 did not know the precise sign which decides the time 

 of growth. 



Flourens has found this sign in the reunion of the 

 bones to their epiphysis. It is at the time when the 

 bones are consolidated to their epiphysis that animals 

 cease to grow. This reunion takes place generally in 

 man at the age of 20 ; in the horse at 5 years ; in the 

 lion at 4, and in the dog at 2 years. Now the horse 

 lives to the age of 25 years, the lion to 20, and the 

 dog to 10 and 12, which makes it nearly five times 

 the length of the growth. Thus the life of man, 

 regular and free from accidents, ought to last a cen- 

 tury at least. 



Flourens, in extending thus the length of life, must 

 be adopting an unusual classification of its different 

 periods. According to him — and his doctrine is the 



