VITAL ENERGY OF MAMMALIA. 5?.1 



several degrees higher, as we have already seen. 

 The consequence of which is, that they are capa- 

 ble of resisting much greater degrees of cold, and 

 of enduring muscular exertion for a much longer 

 time, without exhaustion.* The thorax of the 

 greyhound is larger in proportion to his size, than 

 that of any other quadruped; and it is well known 

 that, for a short distance, he will surpass the 

 swiftest race-horse, that, with a fair field, he will 

 overtake the hare, fox, deer, and rabbit, in a few 

 minutes, during which his speed is equal to that of 

 the wild pigeon, which flies at the rate of a mile 

 every minute for several hours. 



The thorax of the common foxhound is larger, 

 in proportion to his weight, than that of the 



* When I come to treat on the influence of climate and season, 

 food and drink, exercise, repose, &c. it will be shown that the 

 lungs of man and other mammalia, from the greater necessity of 

 exercising them, are more developed in the higher latitudes than 

 in the tropical regions, that they are larger in the dog, wolf, fox, 

 polar bear, reindeer, and other animals which inhabit cold cli- 

 mates, in proportion to the size of the body, than in the elephant, 

 rhinosceros, camel, tiger, leopard, or even the lion, whose tem- 

 perature, muscular activity, and power of enduring cold, are pro- 

 portionally less. It will also be seen that respiration, the power 

 of enduring intense cold, and protracted muscular exertion, a,re 

 greatly diminished by starvation, and that vital heat is expended 

 by over-exertion faster than acquired. As an example of this, it 

 has been said that 30,000 horses belonging to the French army 

 perished in one week, chiefly from cold, during the fatal retreat 

 from Moscow, when the mercury was only 20 below the freezing 

 point of water ; whereas it is certain that, when well fed, and 

 not over-exerted, this noble animal is capable of enduring a tem- 

 perature of 40 or 50 lower, without house or clothing. 



