There is a certain treatise of Aristotle, in which animals are distributed into four kinds, terrestrial, aqueous, fowl, and heavenly; and he calls the stars and the world also animals, yea, and God himself he defines to be an animal endowed with reason and immortal. Democritus and Epicurus esteem all animals rational which have their residence in the heavens. Anaxagoras says that animals have only that reason which is operative, but not that which is passive, which is justly styled the interpreter of the mind, and is like the mind itself. Pythagoras and Plato, that the souls of all those who are styled brutes are rational; but by the evil constitution of their bodies, and because they have a want of a discoursive faculty, they do not act rationally. This is manifested in apes and dogs, which have voice but not speech. Diogenes, that this sort of animals are partakers of intelligence and air, but by reason of the density in some parts of them, and by the superfluity of moisture in others, they enjoy neither understanding nor sense; but they are affected as madmen are, the commanding rational part being defectuous and impeached. CHAPTER XXI. WHAT TIME IS REQUIRED TO SHAPE THE PARTS OF ANIMALS IN THE WOMB. Empedocles believes, that the joints of men begin to be formed from the thirty-sixth day, and their shape is completed in the nine and fortieth. Asclepiades, that male embryos, by reason of a greater natural heat, have their joints begun to be formed in the twenty-sixth day,—many even sooner,—and that they are completed in all their parts on the fiftieth day; the parts of the females are articulated in two months, but by the defect of heat are not consummated till the fourth; but the members of brutes are completed at various times, according to the commixture of the elements of which they consist. CHAPTER XXII. OF WHAT ELEMENTS EACH OF THE MEMBERS OF US MEN IS COMPOSED. Empedocles says, that the fleshy parts of us are constituted by the contemperation of the four elements in us; earth and fire mixed with a double proportion of water make the nerves; but when it happens that the nerves are refrigerated where they meet the air, then the nails are made; the bones are produced by two parts of water and the same of air, with four parts of fire and the same of earth, duly mixed together; sweat and tears flow from the liquefaction of these bodies of ours. CHAPTER XXIII. WHAT ARE THE CAUSES OF SLEEP AND DEATH?