Since an account of the properties of food is a part of the doctrine of Hygiene, we shall add that to the preceding, having premised only a few remarks before delivering the particular rules on this head; for nothing is more indispensably necessary than to be well acquainted with the properties of food. Things of an attenuating power open the pores, and clear away the viscid humours which are impacted in them, and cut and attenuate the thick; but when persevered in as articles of food, they beget serous and bilious superfluities, or, if still longer continued, they render the blood melancholic. One ought therefore to abstain from the continued use of them, and in particular those who are of a bilious temperament; for they only suit with those who have collections of phlegm, and of crude, viscid, and thick humours. Those of incrassating powers are sufficiently nutritious, and, if properly digested in the stomach and liver, they form good blood, but occasion obstructions of the spleen and liver. Of these some have only thick juices, as the dried lentil, but some viscid, as the mallows; and in some they are both thick and viscid, as the testaceous fishes. An attenuating diet is safer than an incrassating for the preservation of health, but yet, as it supplies little nourishment, it does not impart tone or strength to the body. One ought, therefore, to take some moderately nutritious food, when experiencing the effects of a deficient diet. They may do so with the least danger who are given to exercises and can take as much rest as they please. But all those who cannot take exercise before food ought to avoid such things as are incrassating; and those who are of an indolent habit ought by no means to take such food. For complete inactivity is one of the greatest evils for the preservation of health, whereas moderate exercise is particularly good. Those articles of food which are intermediate between the incrassating and the attenuating are the best of all, producing blood of a proper consistency. Such a diet, then, agrees with our bodies, but that which produces a bad chyme ought to be shunned. It is better also to avoid variety of food, more particularly if it consist of contrary qualities; for such things, when taken together, do not digest properly. * * * * *