As wits and virtues are needed to the ruling of kind, so to the perfection thereof needeth needly some spirits, by whose benefit and continual moving, both wits and virtues in beasts are ruled to work and do their deeds. As we speak here of a spirit, a spirit is called a certain substance, subtle and airy, that stirreth and exciteth the virtues of the body to their doings and works. A spirit is a subtle body, by the strength of heat gendered, and in man's body giving life by the veins of the body, and by the veins and pulses giveth to beasts, breath, life, and pulses, and working, wilful moving, and wit by means of sinews and muscles in bodies that have souls. Physicians say that this spirit is gendered in this manner wise. Whiles by heat working in the blood, in the liver is caused strong boiling and seething, and thereof cometh a smoke, the which is pured, and made subtle of the veins of the liver. And turneth into a subtle spiritual substance and airly kind, and that is called the natural spirit. For kindly by the might thereof it maketh the blood subtle. And by lightness thereof it moveth the blood and sendeth it about into all the limbs. And this same spirit turneth to heartward by certain veins. And there by moving and smiting together of the parts of the heart, the spirit is more pured, and turned into a more subtle kind. And then it is called of physicians the vital spirit: because that from the heart, by the wosen, and veins, and small ways, it spreadeth itself into all the limbs of the body, and increaseth the virtues spiritual, and ruleth and keepeth the works thereof. For out of a den of the left side of the heart cometh an artery vein, and in his moving is departed into two branches: the one thereof goeth downward, and spreadeth in many boughs, and sprays, by means of which the vital spirit is brought to give the life to all the nether limbs of the body. The other bough goeth upward, and is again departed in three branches. The right bough thereof goeth to the right arm, and the left bough to the left arm equally, and spreadeth in divers sprays. And so the vital spirit is spread into all the body and worketh in the artery veins the pulses of life. The middle bough extendeth itself to the brain, and other higher parts and giveth life, and spreadeth the vital spirit in all the parts about. The same spirit piercing and passing forth to the dens of the brain, is there more directed and made subtle, and is changed into the animal spirit, which is more subtle than the other. And so this animal spirit is gendered in the foremost den of the brain, and is somewhat spread into the limbs of feeling. But yet nevertheless some part thereof abideth in the aforesaid dens, that common sense, the common wit, and the virtue imaginative may be made perfect. Then he passeth forth into the middle den that is called Logistic, to make the intellect and understanding perfect. And when he hath enformed the