Man’s body is divided among the four elements. For he has in him something of fire, of air, of water, and of earth. There is the quality of earth in the flesh, of moisture in the blood, of air in the breath, of fire in the vital heat. Moreover, the four-fold division of the human body indicates the four elements. For the head is related to the heavens, and in it are two eyes, as it were the luminaries of the sun and moon. The breast is akin to the air, because the breathings are emitted from it as the breath of the winds from the air. The belly is likened to the sea, because of the collection of all the humors, the gathering of the waters as it were. The feet, finally, are compared to the earth, because they are dry like the earth. Further, the mind is placed in the citadel of the head like God in the heavens, to look upon and govern all from a high place.[78] [78] _Diff._, 2, 17, 48. In another passage Isidore tells us that fire has its seat in the liver, and that “it flies thence up to the head as if to the heavens of our body. From this fire the rays of the eyes flash, and from the middle of it, as from a center, narrow passages lead not only to the eyes but to the other senses”.[79] [79] _Diff._, 2, 17, 67. Naturally the four elements play a great part in medicine. They are related to the four humors, blood, yellow bile, black bile, and phlegm. “Each humor imitates its element; blood, air;[80] yellow bile, fire; black bile, earth; phlegm, water. Health depends on the proper blending of these humors.”[81] It appears to have been the belief of the time that the humors possessed each the same qualities as the corresponding element. Medical reasoning might confine itself to the four humors or it might go back of them to the four elements, as in the explanation of vertigo, where the diagnosis indicates, apparently, the transmutation of one element into another. Isidore says: “The _arteriae_ [air passages] and veins produce a windiness in man’s head from a resolving of moisture, and make a whirling in his eyes whence it is called vertigo”.[82] [80] Here blood and the element, air, are related; the passage quoted in the preceding paragraph shows a similar relation between blood and the element water. Such inconsistencies are extremely common. [81] _Etym._, 4. 5. [82] _Etym._, 4, 7, 4. That notions of such a loose, semi-philosophical nature should survive while the solid empirical content of medical science faded away, is characteristic of the decline of thought which culminated in the dark ages. The science of medicine had cut itself loose from concrete things, and attached itself almost exclusively to the vague philosophical conceptions from which even the best Greek thinkers had not been able to free it.