Heat may be applied in two ways, with or without moisture. In the first, it increases action more suddenly, and perhaps more simply. In the second, its effects are more gradual, and are likewise complicated with those of moisture, which certainly is an agent capable of operating on the living system, and generally tends to excite a secretory action, or to give a secretory termination to those increased actions, which are induced by agents operating alongst with it. Dry heat is therefore evidently improper in the inflammatio valida, because it will tend to produce mortification; but, if moisture be conjoined, then the suppurative action is excited. When, however, the action has made an approach to the inflammatio assuefacta, then it may be useful to raise the action simply by dry heat, for a little, before we apply heat and moisture; because, if we apply moisture at first, the progress is more tedious, and the action is less certainly excited[20]. Electricity is similar in its operation to heat and dryness, and may be usefully employed in similar cases; but we must, if we expect any benefit, repeat its operation frequently, and continue each application for a considerable time[21]. [20] From what has been said in the preliminary dissertation, we may understand how moisture should tend to induce a secretion. Agents frequently excite conditions somewhat similar to their general properties: Thus, putrid matter tends to induce the action of descent, and consequent putrefaction. We likewise experimentally find, that, if moisture be applied during a general increased action, it induces perspiration, unless it be conjoined with cold, which lessens the action. [21] The proper way to use electricity, in this case, is to draw scintillæ from the part, the patient being insulated. There are two forms in which we employ heat and moisture, namely, fomentations and poultices. Fomentations[22] have this superiority over poultices, that the same degree of heat is always kept up during their application; whereas, when we use poultices, the heat subsides, as they are renewed only at considerable intervals; but fomentations require longer attendance, and more trouble; and, therefore, are only employed for a short time, and commonly betwixt the intervals at renewing the poultices. [22] Fomentations are made, by applying a soft cloth, dipped in any warm fluid, (commonly water) to the part. Sometimes the cloth is wrung hard, in which case it is chiefly steam which is applied.