be too much discontinued, or to be driven into too narrow pores or passages; and therefore if the spirit be enclosed in a hard or an unctuous and tenacious body (which is not easily divided), it is completely bound, and as it were imprisoned, and gives up its desire to issue forth. And hence we see that metals and stones require a long time for their spirit to go forth, unless either the spirit be excited by fire, or the grosser parts be disunited by strong and corrosive waters. The like reason holds good of tenacious bodies, as gums, except that they are dissolved by a gentler heat. Accordingly hard juices of the body, a tight skin, and the like (which are procured by dryness of aliment, exercise, and coldness of the air) are good for longevity, because they closely confine the spirit and prevent its emission.

RULE XVI.

In oily and fat things, though they be not tenacious, the spirit is detained willingly.

EXPLANATION.

The spirit, if it be neither irritated by antipathy to the body that encloses it, nor fed by too great a similitude of that body, nor solicited or excited by an external body, makes no great effort to go out. And oily bodies are without all these properties; for they are neither so hostile to the spirit as hard bodies, nor so similar as watery bodies, nor in good agreement with the air ambient.

RULE XVII.

A rapid escape of the watery humour preserves the oily longer in its existence.

EXPLANATION.

I have already observed that the watery humours, as being of a like substance to the air, escape sooner; the oily, as having less agreement with the air, later. But since both humours are present in most bodies, it happens that the water does as it were betray the oily; for stealing off gradually it carries that off along with it. Therefore there is nothing better for the preservation of bodies than a gentle drying of them, such as may cause the watery humour to exhale without exciting the oily; for then the oily enjoys its proper nature. And this relates not to the prevention of putrefaction (though that likewise is a consequence), but to the preservation of freshness. And hence it is that gentle frictions and moderate exercises that promote perspiration rather than sweating are very conducive to longevity.

RULE XVIII.

Exclusion of the air contributes to longevity, if you guard against other inconveniences.

EXPLANATION.

I just before observed that the escape of the spirit is a double action, from the appetite of the spirit and of the air. If therefore one of these is removed there is not a little gained; and this is chiefly to be expected from anointings. Notwithstanding it is attended by various inconveniences, the remedies whereof have been noted in the second of our ten operations.

RULE XIX.

Youthful spirits introduced into an old body may shortly turn back the course of nature.

EXPLANATION.

The nature of the spirits is as it were the masterwheel which turns the other wheels in the body of man; and therefore in the intention of longevity it ought to stand first. Moreover there is an easier and more expeditious way of altering the spirits than the other parts. For the operation upon the spirits is twofold; the one by aliment, which is slow and as it were circuitous; the other (itself likewise two-fold) which is sudden, and goes at once to the spirits, — namely, by vapours or by the affections.

RULE XX.

Juices of the body somewhat hard and roscid conduce to longevity.

EXPLANATION.

The reason hereof is plain, seeing I before laid down that hard and oily or roscid bodies are dissipated with difficulty. There is however this difference (as was likewise noted in the tenth operation), that though a nard juice is less easily dissipated, yet it is at the same time less reparable. Here therefore we have a convenience, coupled with an inconvenience, so that nc great matter can be achieved thereby. But a roscid juice satisfies both operations; to this therefore we should more diligently apply ourselves.

RULE XXI.

Whatever penetrates by its rarity, and yet corrodes not by its acrimony, generates roscid juices.

EXPLANATION.

This rule is more difficult to practise than to understand. For it is evident that whatever penetrates well, but yet with a sting or tooth (as all acrid and acid things do), leaves behind it wherever it passes some trace of dryness and separation, so that it indurates the juices and dislocates the parts. But contrariwise, things which penetrate from their rarity alone, as it were by stealth and insinuation, without violence, bedew and irrigate the parts in their passage.

And of these not a few have been set down in the fourth and seventh operations.

RULE XXII.

Assimilation is best performed when all local motion

is at rest.

EXPLANATION.

This rule has been sufficiently explained in the commentary on the eighth operation.

RULE XXIII.

Alimentation from without, at least otherwise than by the stomach, is very beneficial to longevity, if it can be effected.

EXPLANATION.

We see that all things which are performed by nutrition take long circuits, but those done by embracing like substances (as is the case in infusions) require no

long time. Therefore external alimentation would be very useful, and the more so, because in old age the digestive faculties fail; so that if there could be some auxiliary nutritions, by bathings, anointings, or even by clysters, these things conjoined might do much, which single are of less service.

RULE XXIV.

Where the digestion is weak to send forth the aliment, there the outward parts should be comforted, so as to attract it.

EXPLANATION.

This is not the same as was propounded in the preceding rule; for it is one thing to attract the external aliment inwards, and another to attract the internal aliment outwards. But they concur in this, that they both assist the weakness of the internal digestions, though by different ways.

RULE XXV.

All sudden renovation of the body is effected either by the spirits or by emollients.

EXPLANATION.

There are two things in the body, namely, spirits and parts; to both of which the way by nutrition is long; but the way to the spirits by vapours or the affections, and to the parts by emollients, is short. But it is to be carefully observed, that I do not at all confound external alimentation with mollifying; for it is not the intention of emollients to nourish the parts, but only to make them more ready to be nourished.