Erasistratus gives this definition of a fever: A fever is a quick motion of blood, not produced by our consent, which enters into the vessels proper unto the vital spirits. This we see in the sea; it is in a serene calm when nothing disturbs it, but is in motion when a violent preternatural wind blows upon it, and then it rageth and is circled with waves. After this manner it is in the body of man; when the blood is in a nimble agitation, then it falls upon those vessels in which the spirits are, and there being in an extraordinary heat, it fires the whole body. The opinion that a fever is an appendix to a preceding affection pleaseth him. Diocles proceeds after this manner: Those things which are internal and latent are manifested by those which externally break forth and appear; and it is clear to us that a fever is annexed to certain outward affections, for example, to wounds, inflaming tumors, inguinary abscesses. CHAPTER XXX. OF HEALTH, SICKNESS, AND OLD AGE. Alcmaeon says that the preserver of health is an equal proportion of the qualities of heat, moisture, cold, dryness, bitterness, sweetness, and the other qualities; on the contrary, the prevailing empire of one above the rest is the cause of diseases and author of destruction. The efficient cause of disease is the excess of heat or cold, the material cause is superabundance or defect, the place is the blood or brain. But health is the harmonious commixture of the elements. Diocles, that sickness for the most part proceeds from the irregular disposition of the elements in the body, for that makes an ill habit or constitution of it. Erasistratus, that sickness is caused by the excess of food, indigestion, and corruptions; on the contrary, health is the moderation of the diet, and the taking that which is convenient and sufficient for us. It is the unanimous opinion of the Stoics that the want of heat brings old age, for (they say) those persons in whom heat more abounds live the longer. Asclepiades, that the Ethiopians soon grow old, and at thirty years of age are ancient men, their bodies being excessively heated and scorched by the sun; in Britain persons live a hundred and twenty years, on account of the coldness of the country, and because the people contain the fiery element within their bodies; for the bodies of the Ethiopians are more fine and thin, because they are relaxed by the sun’s heat, while they who live in northern countries have a contrary state of their bodies, for they are condensed and robust, and by consequence live the longer. A BREVIATE OF A DISCOURSE, SHOWING THAT THE STOICS SPEAK GREATER IMPROBABILITIES THAN THE POETS. 1. Pindar’s Caeneus hath been taken to task by several, being improbably feigned, impenetrable by steel and impassible in his body, and so Descending into hell without a wound, And with sound foot parting in two the ground.