HEAT, in medicine. Great heats are not so much the immediate, as the remote, cause of a general sickness, by relaxing the fibres, and disposing the juices to putrefaction; especially among soldiers and persons exposed the whole day to the sun: for the greatest heats are seldom found to produce epidemic diseases, till the perspiration is stopped by wet clothes, fogs, dews, damps, &c. and then some bilious or putrid distemper is the certain consequence, as fluxes and ardent intermitting fevers. Nevertheless, it must be allowed, that heats have sometimes been so great as to prove the more immediate cause of particular disorders; as when centinels have been placed without cover or frequent reliefs in scorching heats; or when troops march or are exercised in the heat of the day; or when people imprudently lie down and sleep in the sun. All these circumstances are apt to bring on distempers, varying according to the season of the year. In the beginning of summer, these errors produce inflammatory fevers; and in autumn, a remitting fever or dysentery. To prevent, therefore, the effects of immoderate heats, commanders have found it expedient so to order the marches, that the men come to their ground before the heat of the day; and to give strict orders, that none of them sleep out of their tents, which, in fixed encampments, may be covered with boughs to shade them from the sun. It is likewise a rule of great importance to have the soldiers exercised before the cool of the morning is over; for by that means not only the sultry heats are avoided, but the blood being cooled, and the fibres braced, the body will be better prepared to bear the heat of the day. Lastly, in very hot weather, it has often been found proper to shorten the centinels duty, when obliged to stand in the sun.