418 ANIMAL HEAT. [CHAP. xxx. 



M. Hubert, in the Isle of France, encircled a thermometer with 

 twelve spikes of the arum cordifolium, and found it rise to 121 F., 

 the temperature of the external air being 66. During the process 

 of flowering, the spathe of the arum maculatum consumed in 24 

 hours five times its volume of oxygen derived from the surrounding 

 atmosphere, the termination of the spadix 30 times, and the sexual 

 apparatus 132 times its volume, in the same period. In these 

 experiments it was found, that if the plant was protected from the 

 influence of the surrounding air, the development of heat ceased. 

 In the germination of seeds, the starch is converted into gum or 

 dextrine, and ultimately into sugar. The sugar then disappears, 

 while oxygen is absorbed from the air, and carbonic acid evolved. 

 The temperature at the same time rises. 



In these examples, the disappearance of the starch and saccharine 

 matters from the plant, the absorption of oxygen, the formation of 

 carbonic acid, and the development of heat are all manifestly 

 connected. A corresponding series of phenomena attends the de- 

 velopment of heat in animals. 



Development of Heat in Animals. It is to be observed, in the first 

 place, that as all animals give out carbonic acid in their respiration, 

 so all develop heat, whether they are called cold-blooded (reptiles 

 and all below them), or warm-blooded (mammalia and birds). The 

 cold-blooded animals are those which develop so little heat, form 

 and give out so little carbonic acid, that they are unable to main- 

 tain a temperature much removed from that of the medium in 

 which they live ; and their circulatory and breathing organs are 

 entirely accordant with this feeble calorifacient power. Dr. John 

 Davy, who has made a number of valuable and exact observations 

 on this subject, found that when the average temperature around 

 was 79'7 F., that of reptiles was only 82, and that of fishes nearly 

 the same. In the case of insects, Crustacea, and mollusca, there is 

 even a closer correspondence with the temperature of the circum- 

 ambient medium. Insects, however, especially when housed in 

 communities, so that their heat is not rapidly dissipated, have 

 shown a rise of 20 F. above the outward air provided they were 

 in a state of active movement. On this point, the observations of 

 Mr. Newport are very valuable. On the other hand, warm-blooded 

 animals (birds and mammalia), are those in which nutrition with 

 all its attendant accessory functions, assimilation, circulation, 

 respiration, the supply of food, and of oxygen, the formation and 

 disengagement of carbonic acid are most active and energetic. 

 These have a nearly uniform temperature within the limits of 96 



