spects, remedies adapted to continued fevers. Those especially in use are, the vitriolic and vegetable; and, on many accounts, we prefer the latter.

135. Another set of refrigerants are, the neutral salts, formed of the vitriolic, nitrous, or vegetable acids; with alkalines, either fixed or volatile. All these neutrals, while they are dissolving in water, generate cold; but as that cold ceases soon after the solution is finished, and as the salts are generally exhibited in a dissolved state, their refrigerant power in the animal body does not at all depend upon their power of generating cold with water. The neutral chiefly employed as a refrigerant, is nitre; but all the others, compounded as above mentioned, partake more or less of the same quality.

136. Beside these neutrals, some metallic salts also have been employed as refrigerants in fevers; and particularly the sugar of lead. But the refrigerant powers of this are not well ascertained; and its deleterious qualities are too well known to admit of its being freely used.

137. Under the third general head (128, 3) of the means to be employed for moderating the violence of reaction, are comprehended the several means of diminishing the tension, tone, and activity of the sanguiferous system. As the activity

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of this system depends, in a great measure, upor the tone, and this again upon the tension of the vessels, given to them by the quantity of fluids they contain, it is evident, that the diminution of the quantity of these must diminish the activity of the sanguiferous system.

138. The quantity of fluids contained in the sanguiferous system, may be diminished most conveniently by the evacuations of blood-letting and purging.

139. Nothing is more evident than that bloodletting is one of the most powerful means of di minishing the activity of the whole body, especially of the sanguiferous system; and it must therefore be the most effectual means of moderating the vio lence of reaction in fevers. Taking this as a fact, I omit inquiring into its mode of operation, and shall only consider in what circumstance of fevers it may be most properly employed.

140. When the violence of reaction, and its constant attendant, a phlogistic diathesis, are sufficiently manifest; when these constitute the principal part of the disease, and may be expected to continue throughout the whole of it, as in the cases of synocha; then blood-letting is the principal remedy, and may be employed as far as the symptoms of the disease may seem to require, and the consti

tution of the patient will bear. It is, however, to be attended to, that a greater evacuation than is necessary, may occasion a slower recovery, may render the person more liable to a relapse, or may bring on other diseases.

141. In the case of synocha, therefore, there is little doubt about the propriety of blood-letting; but there are other species of fever, as the synochus, in which a violent reaction and phlogistic diathesis appear, and prevail during some part of the course of the disease; while, at the same time, these circumstances do not constitute the principal part of the disease, nor are to be expected to continue during the whole course of it; and it is well known, that, in many cases, the state of violent reaction is to be succeeded, sooner or later, by a state of debility, from the excess of which the danger of the disease is chiefly to arise. It is therefore necessary, that, in many cases blood-letting should be avoided; and even although, during the inflammatory state of the disease, it may be proper, it will be necessary to take care that the evacuation be not so large as to increase the state of debility which is to follow.

142. From all this it must appear that the employing blood-letting, in certain fevers, requires much discernment and skill, and is to be governed by the consideration of the following circumstances,

1, The nature of the prevailing epidemic.

2, The nature of the remote cause.

3, The season and climate in which the disease

Occurs.

4, The degree of phlogistic diathesis 5, The period of the disease.

present.

6, The age, vigour, and plethoric state of the patient.

7, The patient's former diseases and habits of blood-letting.

8, The appearance of the blood drawn out.

9. The effects of the blood-letting that may have been already practised.

143. When, after the consideration of these circumstances, blood-letting is determined to be necessary, it should be observed, that it is more ef fectual, according as the blood is more suddenly drawn off, and as the body is at the same time more free from all irritation, and consequently when in a posture in which the fewest muscles are in action.

144. Another evacuation whereby the quantity of fluids contained in the body can be considerably diminished, is that of purging.

145. If we consider the quantity of fluids constantly present in the cavity of the intestines, and the quantity which may be drawn from the in

numerable excretories that open into this cavity, it will be obvious, that a very great evacuation can be made by purging; and, if this be done by a stimulus applied to the intestines, without being at the same time communicated to the rest of the body, it may, by emptying both the cavity of the intestines, and the arteries which furnish the excretions poured into it, induce a considerable relaxation in the whole system; and therefore purging seems to be a remedy suited to moderate the violence of reaction in fevers.

146. But it is to be observed, that, as the fluid drawn from the excretories opening into the intestines, is not all drawn immediately from the arteries, as a part of it is drawn from the mucous follicles only; and as what is even more immediately drawn from the arteries, is drawn off slowly; so the evacuation will not, in proportion to its quantity, occasion such a sudden depletion of the red vessels as blood-letting does; and therefore cannot operate so powerfully in taking off the phlogistic diathesis of the system.

147. At the same time, as this evacuation may induce a considerable degree of debility; so, in those cases in which a dangerous state of debility is likely to occur, purging is to be employed with a great deal of caution; and more especially as the