ANIMAL HEAT. 395 



what shaken by the consideration, that many of the so-called cold- 

 blooded animals from the agility of their movements, the nature 

 of their food, their respiratory equivalents, the energy of their 

 growth and nutrition, in short, from the amount of their metamor- 

 phosis of matter, are not so far different from mammals and birds 

 as to establish the necessity of this high degree of temperature for 

 the maintenance of life, and the energetic performance of the most 

 essential vital functions. And are we not arguing in a circle, when 

 we assert that animal heat is subservient to the metamorphosis of 

 matter, and that the latter again is subservient to the promotion of 

 animal heat ? If we were to assume, that this high degree of tem- 

 perature is necessary for the formation of the tissues from nitroge- 

 nous food, as well as for the functions of the organs, and that 

 amylaceous substances are taken up in the organism merely for the 

 purpose of generating this degree of temperature, the cold-blooded 

 animals, which are not inferior to higher animals in rapidity of 

 growth, and not unfrequently equal them in the energy of their 

 vital functions, would, even under such limitations, refute these 

 conclusions. If the carbo-hydrates were consumed by animals 

 merely for the purpose of generating heat, it seems teleologically 

 incomprehensible why certain fishes, whose animal heat never rises 

 above the surrounding medium, even after the most active move- 

 ments, should live almost exclusively upon amylaceous matters. 

 (We need only instance the case of gold-fishes, which live for years 

 on no other food than wafers.) We have already endeavoured 

 (pp. 216-221) to indicate the objects which may be fulfilled by 

 the carbo-hydrates beyond that of generating heat in the animal 

 body. We do not, however, intend by these remarks to disparage 

 the importance of animal heat in relation to life. All the admi- 

 rable investigations which have led us to recognise an internal con- 

 nection between respiration, certain nutrient matters, and animal 

 heat, have afforded us a deeper insight into the vital processes ; and 

 hence it is no poetical imagery to connect the life of respiring 

 beings in reference to their production of heat with the process of 

 combustion. Animal heat does not, however, on that account 

 occupy a higher place than every other phenomenon, and every 

 other result which is manifested in the active living organism ; at 

 once an effect and a cause, it proceeds, as in combustion, from pro- 

 cesses on which it exerts a favourable reflex action ; it is only one, 

 but not the highest link of that immeasurable series of phenomena 

 which constitute the true substance of corporeal existence, and is 



