226 THE PHENOMENA OF MOTION 



bear a fixed relation to the amount of oxygen which 

 can be absorbed in a given time by the animal body. 



The quantities of oxygen which a whale and a carri- 

 er's horse can inspire in a given time are very unequal. 

 The temperature, as well as the quantity of oxygen, 

 is much greater in the horse. 



The force exerted by a whale, when struck with the 

 harpoon, his body being supported by the surrounding 

 medium, and the force exerted by a carrier's horse, 

 which carries its own weight and a heavy burden for 

 eight or ten hours, must both bear the same ratio to the 

 oxygen consumed. If we take into consideration the 

 time during which the force is manifested, it is obvious 

 that the amount of force developed by the horse is far 

 greater than in the case of the whale. 



In climbing high mountains, where, in consequence 

 of the respiration of a highly rarefied atmosphere, much 

 less oxygen is conveyed to the blood, in equal times, 

 than in valleys or at the level of the sea, the change of 

 matter diminishes in the same ratio, and with it the 

 amount of force available for mechanical purposes. 

 For the most part, drowsiness and want of force for 

 mechanical exertions come on ; after twenty or thirty 

 steps, fatigue compels us to a fresh accumulation of 

 force by means of rest (absorption of oxygen without 

 waste of force in voluntary motions) . 



By the absorption of oxygen into the substance of 

 living tissues, these lose their condition of life, and are 

 separated as lifeless, unorganized compounds ; but the 



