Chap, i.] OF ORGANIC HEAT. 445 



Nobili and Melloni, taking observations witli a thermo-electric 

 apparatus, have always found in insects a positive temperature 

 of a fraction of a degree, or even of some degrees. Edaumur 

 observed in a beehive a positive temperature of 12°, 5, when the 

 thermometer marked 3°,75 outside it.^ 



But if the temperature of invertebrated animals almost always 

 preserves a more or less notable excess over the outer temperature, 

 it varies, absolutely, in very large proportions. Ordinarily, it 

 follows, more or less readily the exterior thermometric oscillations, 

 rising in the day in summer, falling at night in winter. During 

 the latter season, and in cold climates, most invertebrated animals 

 which are not killed by the lowness of the temperature become 

 benumbed, and fall into hibernation, subject as they are tc 

 climateric vicissitudes. 



That which we have just said of invertebrated animals might 

 almost be applied to the two lower classes of the vertebrates, 

 like the invertebrated animals, fishes and reptiles have a 

 temperature which varies with that of the ambient medium, 

 whilst generally higher than the latter j like the invertebrated 

 animals again, most of them are benumbed in winter. Never- 

 theless, their overplus of temperature is habitually higher than 

 that of the invertebrated animals. Moreover, it is very variable. 

 In fishes it has sometimes been found to be only 0°,20, sometimes 

 3°,88. In the fishes of the Sea of Marmora, Davy has even 

 observed a thermal excess much more considerable. In taking 

 the temperature of the abdomen and that of the dorsal muscles, 

 he has found the former 6°,11, and the second 7°, 22. in excess 

 of that of the sea. 



In reptiles the surplus temperature may sometimes be stated 

 as stiU greater; though sometimes only 0°-04 in the frog, it 

 has been seen to rise to 8°',12 in the Zacerto agilis. 



In the vertebrated animals of the two higher classes, in birds 



1 Censnlt J. Gavairet,. ie« P^nomSmes Phyaiologigpus de la Vie, and the 

 article on " Chaleur Animale," in the Dictionaire EncyclopSdique des Sciences 



