446 BIOLOGY. [Book vii, 



and> mammifers, where the respiratory and circulatory systems 

 are better constructed, where the two kinds of blood are not 

 mingled, where respiration is more active, the organic tempera- 

 ture shakes off in some degree the yoke of the outer temperature, 

 and if we except some rare species, which are still subject to 

 hibernation, it is proved that the superior vertebrates enjoy a 

 temperature of their own tolerably high, and only varying to a 

 small extent, in spite of climates and seasons. The temperature 

 of adult and well-fed birds varies from 38 to 45 degrees. This 

 variation of some degrees corresponds with specific, individual, 

 even sexual differences ; in fact, Professor Martins has seen, in 

 the duck species, that the temperature of the female was sensibly 

 higher and also more variable than that of the males. 



The temperature of the mammifers is lower by some degrees 

 than that of birds, but is invariable, like this latter. Thus, in 

 the Arctic regions. Parry has found the temperature of a fox 

 exceed the ambient medium by 76°,7. 



The temperature of the ambient medium oscillates between 36 

 and 40 degrees. That of man varies between 36°,50 and 37°,50, 

 and differs according to age and sex ; it is higher in the child 

 than in the adult, higher in the adult than in the menstruous 

 woman, and lower perceptibly in the old man, during sleep, 

 &c., &c., besides following with sufficient fidelity the oscillations 

 of the respiratory energy. (See Book II., Chap, xiv.) 



From the series of facts which we have just enumei'ated, it 

 results that there are no cold-blooded animals in the literal sense 

 of the expression, and neither are there any animals with an 

 invariable temperature in the strict meaning of the word. In the 

 whole animal king,dom, the organic temperature, and especially 

 that of the blood, is normally higher than the exterior tempera- 

 ture. Moreover in the whole animal kingdom the, organic 

 temperature oscillates and varies. But these thermic variations 

 decrease in proportion as the animal is higher in the ' series, and 

 in the well-nourished bird and mammif er, the temperature of the 

 interior medium, the blood, only varies within narrow, limits ; 



