THE DISEASES OF CATTLE. * 321 



"It is obvious that the cause of the generation of force, 

 namely, the change of matter, is diminished, because, with the 

 abstraction of heat, as in the plant by abstraction of light, the 

 intensity of the vital force diminishes. It is also obvious that 

 the momentum of force in a living part depends on its proper 

 temperature ; exactly as the effect of a falling body stands in 

 a fixed relation to certain other conditions ; for example, to the 

 velocity attained in falling. 



" When the temperature sinks, the vital energy diminishes ; 

 when it again rises, the momentum of force in the living parts 

 appears once more in all its original intensity. 



" The production of force for mechanical purposes, and the 

 temperature of the body, must, consequently, bear a fixed rela- 

 tion 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 carrier's 

 horse can inspire in a given time are very unequal. The tem- 

 perature, as well as the quantity of oxygen, is much greater 

 in the horse. 



" The force exerted by a whale, when struck with the har- 

 poon, 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 availaljle for me- 

 chanical 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)." 



