By this expression is meant a diminution of the quantity of blood, arising from a diminished supply of nutritive material, calculated to repair the waste incurred in the support of the functions. if the blood is expended in nutrition, respiration, and other vital processes, and receives insufficient supplies through the digestive and absorbent functions, it must suffer a diminution, if not in bulk, at least in the proportion of its solid organic constituents. The same effects are produced upon it as result, in the end, from direct depletion. it becomes less stimulant and nutritive to the functions, which are consequently depressed in the same manner as by the loss of blood, though less rapidly. The remarks, moreover, before made in relation to the frequent nervous irritation, and circulatory and respiratory excitement, resulting from an impoverished state of the blood, and to the principles upon which these effects are produced, are not less applicable to the consequences of indirect than to those of direct depletion. it is unnecessary, therefore, to repeat them in this place.

Indirect depletion is effected in two ways; 1. by removing from the stomach and bowels the nutritious material which may have been swallowed, and in a greater or less degree digested, before it has had the opportunity of entering the circulation; and 2. by lessening the amount or lowering the quality of the food admitted into the stomach. The first end is attained by means of emetics and cathartics, which are, therefore, doubly depletory; to wit, directly, by promoting secretion from the blood, and indirectly, in the method here referred to. This subject will be treated of under the two classes of medicines mentioned. it is the second method only with which we are concerned at present. in this, there may be entire abstinence from food, or simply a diminution of its quantity, or an alteration of its character; or the two latter conditions may be combined.

1. Abstinence. Entire abstinence from food can be tolerated only when the appetite is wanting. if it be attempted, as a sedative measure, when the digestive function is in good order, and the system calls for food, though great prostration may occur, and even death result, yet the symptoms exhibited in the progress of the starvation will be anything else than purely sedative. The wants of the functions call imperiously upon the nervous centres; these express their own suffering by an intense sensation of hunger, while the heart is excited to send the diminishing blood in a more rapid current through the organs; and, if no relief is afforded, both the animal and organic functions are thrown into great disorder, and delirium and low fever not unfrequently precede death. Entire abstinence, therefore, cannot be safely resorted to as a sedative agent, under the circumstances mentioned. But for a day or two, in the early stage of severe inflammation, or high fever, when there is an aversion instead of desire for food, it may be proper to obey the pointing of nature, and to withhold nutriment in every shape, allowing the patient only pure cold water. Longer than this, it will seldom, I think, be proper to persevere in the exclusive method, even though the want of desire for food should continue. The starving plan, in inflammations and fevers, may counteract the very object it is intended to serve. The functions are not quiescent in these affections. They are constantly in exercise, in a greater or less degree, and constantly consuming blood. in the absence of any supply through the digestive organs, the circulation must depend upon the material thrown into it through the absorbents, or entering the venous radicles, derived from the disintegration of the tissues. This of course is animal food in a highly concentrated form, and probably not always in the best state of preparation. The blood is thus rendered impure, and becomes irritant; and, instead of a simple sedative effect being experienced, it is probable that the inflammation and the fever are increased. Nutritive matter should, therefore, be supplied, at first of the blandest character and feeblest sustaining power, and afterwards improved in both these respects, as the disease advances, and the system may more need support.

2. Diminution Simply of the Quantity of Food. This is undoubtedly sedative in its tendency, unless the diminution be so great as to excite the reactive influences above explained. in health it may, perhaps, be considered as purely sedative. But, in diseases of excitement, a mere abstraction of a portion of the diet ordinarily used in health, without a change in its character, is not all that the circumstances require. Supposing it to be of the usual mixed character, partly animal and partly vegetable, it will often be found to stimulate the system injuriously even in very small quantity. There is something in the flesh of animals, used as food, that is more than purely nutritious. There is something essentially stimulating to the system, quite independently of any immediate effects on the digestive organs. Even in health this may be observed to a considerable extent. Any one who will count his pulse and observe his feelings after a meat dinner, will find the former more frequent, and the latter in various ways evincive of a higher excitation, than when the meal is confined to vegetables or even milk. I have often noticed this in my own personal experience. In diseases of excitement the difference is still greater. How often is the attention of the physician arrested, in his visits, by some aggravation of inflammation or fever, which he is enabled to trace, by his inquiries, to the forbidden use of animal food ! Even a small quantity, quite insufficient, by its mere nutritive matter, to produce any sensible impression, will be found sufficient to increase the frequency of the pulse and heat of skin, as though the patient had been taking wine. How much more stimulant, for example, is a little soup, than an equal quantity of gruel, though the latter may contain a larger amount of assimilable matter ! In employing diet, therefore, as a sedative agent in disease, it is necessary not merely to lessen the quantity, but to abstract from it the animal ingredients, either wholly or in part, according to the degree of sedative influence required..