306 Dr. Edwards,- De finflumce 



taneously affected. Among reptiles, Dr. Edwards found 

 that life could be maintained by this dark blood ; but it is 

 questionable whether the circulation of venous or dark 

 blood can promote life in animals of the warm-blooded kind. 

 Temperature certainly modifies their capability of existence. 

 Under 20°, they live longest ; at 0°, their existence is 

 shortest. The vitality of the nervous system seems to be 

 thus directly influenced by temperature. 



Of all the phenomena of animal life, those relative to the 

 blood's state in asphyxia are, perhaps, the most interesting and 

 cui'ious, from the loss of consciousness, sensation, and volun- 

 tary motion attending its disoxygenated state. If, however* 

 animals differ so materially under the influence of ^ deprivation 

 of air, as to the duration of such existence, we may imagine a 

 corresponding difference relative to their respirations modi- 

 fied by species, age, &c. Air, the pabulum vitce, is not 

 equally consumed, by all, but in different proportions; at 

 least, such is the presumption from the experiments upon 

 animals of warm blood. The relative proportions of this 

 difference are sought to be ascertained. Warm-blooded 

 animals of equal size and age, at their liveliest period of age, 

 were the objects of comparative inquiry. We must refer 

 the reader to the table at the end of the work for the results. 

 A marked difference is observable between the quantity of 

 air consumed by the cold-blooded animals and that required 

 for the support of the warm-blooded ; and each has an orga- 

 nization appropriated to the individual distinctions. Thus 

 the structure of the reptile and fish entails the lesser con- 

 sumption of air, compared with that of the mammiferae and 

 birds. Fish consume least air, reptiles stand next, then the 

 mammiferae, and, lastly, birds consume most. The two last, 

 however, very nearly approach each other ; so do also the 

 two first ; and the distinction between the organization and 

 the consumption of air is most strongly marked betv/een the 

 fish and reptiles on the one hand, and the mammiferse and 

 birds on the other, which, indeed, has caused their separation 

 into two distinct groups, by the appellation of cold and warm 

 blooded animals, — a distinction which clearly separates the 

 whole of the vertebrated animals into two groups, bearing 

 different physiological characters in their relations to animal 

 heat and respiration. 



The mere temperature of the blood in each group is insuf- 

 ficient for our knowledge of their distinctive characters. We 



