Note 3 — ANIMAL HEAT.

Animals are divided by naturalists into two classes, cold-blooded and warm-blooded; the latter breathe by lungs, through which all the blood of the body is continually passed, and which has direct communication with the air. Cold-blooded creatures, such as fishes, breathe by means of gills, and the air, instead of coming into direct contact with their vital fluid, is absorbed from the water. In the case of reptiles, which are cold-blooded, although the air may come into direct contact with the blood, as in the respiration of the frog, yet, by the peculiar structure of his lungs, only half the blood is sent to them to be purified; and thus his superiority over the fish in receiving air direct, is balanced by the circumstance that his blood is only half purified, in consequence of being only in part exposed to the action of the air. The temperature of animals is found to have relation to their activity and vital energy. The following list exhibits the temperature of the animals mentioned.—

Birds, 105 degrees Fahrenheit,

Sheep, 100 degrees —

Worms, 36 degrees —

Frog, 40 degrees —

Snail, 36 degrees —

Fish, 60 degrees —