due measure of the evacuation is more difficult to be applied than in the case of blood-letting,

148. As we shall presently have occasion to observe, that it is of great importance, in the cure of fevers, to restore the determination of the blood to the vessels on the surface of the body; so purging, as in some measure taking off that determination, scems to be an evacuation not well adapted to the cure of fevers.

149. If, notwithstanding these doubts, (146, 147, and 148), it shall be asserted, that purging, even from the exhibition of purgatives, has often been useful in fevers; I would beg leave to main, tain, that this has not happened from a large eva cuation; and, therefore, not by moderating the violence of reaction, excepting in the case of a more purely inflammatory fever, or of exanthe, mata of an inflammatory nature. In other cases of fever, I have seen a large evacuation by purging, of mischievous consequence; and if, upon occasion, a more moderate evacuation has appeared to be useful, it is apprehended to have been only by taking off the irritation of retained feces, or by evacuating corrupted humours which happened to be present in the intestines; for both of which purposes, frequent laxatives may be properly em, ployed.

150. Another set of means (127, 2) for moderating the violence of reaction in fevers, are those suited to take off the spasm of the extreme vessels, which we believe to be the irritation that chiefly supports the reaction.

Though I have put here this indication of taking off the spasm of the extreme vessels, as subordinate to the general indication of moderating the violence of reaction; it is however to be observed here, that as fever universally consists in an increased action of the heart, either in frequency or in force, which in either case is supported by a spasm of the extreme vessels, so the indication for removing this is a very general one, and applicable, in almost every circumstance of fever, or at least with a few exceptions, to be taken notice of hereafter.

151. For taking off the spasm of the extreme vessels, the means to be employed are either internal or external.

152. The internal means (151) are,

1, Those which determine the force of the circulation to the extreme vessels on the surface of the body, and, by restoring the tone and activity of these vessels, may overcome the spasm on their extremities.

2, Those medicines which have the power of taking off spasm in any part of the system, and which are known under the title of ANTISPASMODICS.

153. Those remedies which are fit to determine to the surface of the body, are,

1, DILUENTS;

2, NEUTRAL SALTS;

3, SUDORIFICS; 4, EMETICS.

154. Water enters, in a large proportion, into the composition of all the animal fluids, and a large quantity of it is always diffused through the whole of the common mass. Indeed, in a sound state, the fluidity of the whole mass depends upon the quantity of water present in it. Water, therefore, is the proper diluent of our mass of blood; and other fluids are diluent only in proportion to the quantity of water they contain.

155. Water may be said to be the vehicle of the several matters which ought to be excerned; and in a healthy state the fulness of the extreme vessels, and the quantity of excretions, are nearly in proportion to the quantity of water present in the body. In fever, however, although the excretions are in some measure interrupted, they continue in such quantity as to exhale the more fluid parts of the blood; and while a portion of them is at the same time necessarily retained in the larger vessels, the smaller and the extreme vessels, both from the deficiency of fluid, and their own contracted state, are less

filled, and therefore allowed to remain in that condition.

156. To remedy this contracted state, nothing is more necessary than a large supply of water or watery fluids, taken in by drinking or otherwise ; for as any superfluous quantity of water is forced off by the several excretories, such a force applied may be a means of dilating the extreme vessels, and of overcoming the spasm affecting their extremities.

157. Accordingly, the throwing in of a large quantity of watery fluids has been, at all times, a remedy much employed in fevers; and in no instance more remarkably, than by the Spanish and Italian physicians, in the use of what they call the Diæta aquea.

158. This practice consists in taking away every other kind of aliment and drink, and in giving in divided portions every day, for several days together, six or eight pounds of plain water, generally cold, but sometimes warm. All this, however, is to be done only after the disease has continued for some time, and, at least, for a week.

159. A second means (153, 2) of determining to the surface of the body, is by the use of neutral salts. These, in a certain dose taken into the

stomach, produce soon after a sense of heat upon the surface of the body; and, if the body be covered close and kept warm, a sweat is readily brought out. The same medicines, taken during the cold stage of a fever, very often put an end to the cold stage, and bring on the hot; and they are also remarkable for stopping the vomiting which so frequently attends the cold stage of fevers. All this shews, that neutral salts have a power of determining the blood to the surface of the body, and may therefore be of use in taking off the spasm which in feyer subsists there,

160. The neutral most commonly employed in fevers, is that formed of an alkali with the native acid of vegetables: but all the other neutrals have more or less of the same virtue; and perhaps some of them, particularly the ammoniacal salts, possess it in a stronger degree.

161. As cold water taken into the stomach of ten shews the same diaphoretic effects with the neutral salts, it is probable that the effect of the latter depends upon their refrigerant powers mentioned above (134). What is the effect of the neutral salts, given when they are forming and in a state of effervescence? It is probable that this circumstance may increase the refrigerant power of these salts, and may introduce into the body a quantity of fixed air; but for these purposes it