SECT. XVIII.—ON THE KINDS OF FRICTION.
Hard friction contracts, and soft relaxes; so that those persons that are relaxed should be rubbed hard, and those that are immoderately constricted, softly; and when, neither in the one state nor the other, it is clear that neither the one mode of friction nor the other should be had recourse to, but as much as possible either extreme ought to be avoided. For much and hard friction diminishes the bulk of the body, whilst, on the other hand, little and soft distends it. If the three different kinds of frictions as to quantity be joined to the same number as to quality, they will produce nine combinations, as is stated below. For one of the kinds, as to quantity, for example much, being complicated with the three differences as to quality, I mean the hard, the soft, and the moderate as to hardness, will produce three combinations; and, again, the little being joined to the other three will produce three more; and the moderate as to quality being complicated with the same three, will produce three more, as is shown below:
| QUANTITY. | QUALITY. | |||
| Much | } | and | { | Hard. |
| Much | } | { | Soft. | |
| Much | } | { | Moderate. | |
| Little | } | and | { | Hard. |
| Little | } | { | Soft. | |
| Little | } | { | Moderate. | |
| Moderate | } | and | { | Hard. |
| Moderate | } | { | Soft. | |
| Moderate | } | { | Moderate. | |
Commentary. The brief but comprehensive rules of Hippocrates for the application of friction, are thus given in the language of Celsus: “Hippocrates dixit, frictione, si vehemens sit, durari corpus; si lenis, molliri; si multa, minui; si modica, impleri.” Celsus adds, that, according to circumstances, the body may be braced by it, if relaxed; may be softened, if indurated; may have its superfluities expelled, if loaded with plethora; and have nourishment attracted to it, if emaciated. He remarks, that it is mostly applicable in the decline of a disease. His other directions for the application of it are very apposite, (ii, 14.)
Pliny delivers the rules of Hippocrates in nearly the same words as Celsus. (Hist. Nat. xxviii, 14.)
Our author’s account of friction is taken from Oribasius (Med. Collect. vi), or from Aëtius (iii.) All, however, are indebted to Galen, who handles the subject most scientifically. (Hyg. ii.)
Similar directions are given by Avicenna (i, 3, 2), and by Haly Abbas (Theor. v, 12.) Averrhoes gives the sum of the directions laid down by Galen and the other authorities. Strong friction, he says, braces and hardens the body; weak, rarifies and softens; moderate, operates in an intermediate degree. Besides, he adds, hard friction diminishes obesity; moderate, on the other hand, tends to remove emaciation. (Collect. ii, 3.)
It was a general practice of the ancients to have recourse to friction in the morning and evening. Oribasius has many excellent observations on this practice. (l. c.)