general knowledge, in connection with the rabbit's life-activity. In a day of the rabbit's life a considerable amount of work is done-- the animal runs hither and thither, for instance; in other words, a certain mass of matter is moved through space, and for that we know force must be exerted. Whence comes the force?
Text Book of Biology, Part 1: Vertebrata · The Wunder Library — complete classics, free to read, with narration.