tary substances into this organ. It may, therefore, be said that the sensation of hunger is caused both by a want in the system generally, and also by the condition of the stomach itself, by which condition, of course, its own nerves are more directly affected.

:

The sensation of thirst, indicating the want of fluid, is referred to the fauces, although, as in hunger, this is, in great part, only the local declaration of a general condition. For thirst is relieved for only a very short time by moistening the dry fauces; but may be relieved completely by the introduction of liquids into the blood, either through the stomach, by injections into the bloodvessels, or by absorption from the surface of the skin or the intes tines. The sensation of thirst is perceived most naturally whenever there is a disproportionately small quantity of water in the blood as well, therefore, when water has been abstracted from the blood, as when saline or any solid matters have been abun dantly added to it. And the cases of hunger and thirst are not the only ones in which the mind derives, from certain organs, a peculiar predominant sensation of some condition affecting the whole body. Thus, the sensation of the "necessity of breathing." is referred especially to the air-passages; but, as Volkmann's experiments show, it depends on the condition of the blood which circulates everywhere, and is felt even after the lungs of animals are removed; for they continue, even then, to gasp and manifest the sensation of want of breath.

Starvation. The effects of total deprivation of food have been made the subject of experiments on the lower animals, and have been but too frequently illustrated in man. (1.) One of the most notable effects of starvation, as might be expected, is loss of weight; the loss being greatest at first, as a rule, but afterwards not varying very much, day by day, until death ensues. Chossat found that the ultimate proportional loss was, in different animals experimented on, almost exactly the same; death occurring when the body had lost two-fifths (forty per cent.) of its original weight. Different parts of the body lose weight in very different proportions. The following results are taken, in round numbers, from the table given by M. Chossat:

(2.) The effect of starvation on the temperature of the various animals experimented on by Chossat was very marked. For some time the variation in the daily temperature was more marked than its absolute and continuous diminution, the daily fluctuation amounting to 5° or 6° F. (3° C.), instead of 1° or 2° F. (5° to 1° C.), as in health. But a short time before death, the temperature fell very rapidly, and death ensued when the loss had amounted to about 30° F. (162° C.). It has been often said, and with truth, although the statement requires some qualification, that death by starvation is really death by cold; for not only has it been found that differences of time with regard to the period of the fatal result are attended by the same ultimate loss of heat, but the effect of the application of external warmth to animals cold and dying from starvation, is more effectual in reviving them than the administration of food. In other words, an animal exhausted by deprivation of nourishment is unable so to digest food as to use it as fuel, and therefore is dependent for heat on its supply from without.

(3.) The symptoms produced by starvation in the human subject are hunger, accompanied, or it may be replaced, by pain, referred to the region of the stomach; insatiable thirst; sleeplessness; general weakness and emaciation. The exhalations both from the lungs and skin are fætid, indicating the tendency to decomposition which belongs to badly-nourished tissues; and death occurs, sometimes after the additional exhaustion caused by diarrhoea, often with symptoms of nervous disorder, delirium or convulsions.

(4.) In the human subject death commonly occurs within six to ten days after total deprivation of food. But this period may be considerably prolonged by taking a very small quantity of food, or even water only. The cases so frequently related of survival after many days, or even some weeks, of abstinence, have been due either to the last-mentioned circumstances, or to others no less effectual, which prevented the loss of heat and moisture. Cases in which life has continued after total abstinence from food and drink for many weeks, or months, exist only in th imagination of the vulgar.

(5.) The appearances presented after death from starvation are those of general wasting and bloodlessness, the latter condition being least noticeable in the brain. The stomach and intestines are empty and contracted, and the walls of the latter appear remarkably thinned and almost transparent. The various secretions are scanty or absent, with the exception of the bile, which, somewhat concentrated, usually fills the gall-bladder. All parts of the body readily decompose.

II.-Effects of Improper Diet.

Experiments on Feeding.-Experiments illustrating the ill-effects produced by feeding animals upon one or two alimentary substances only have been often performed.

Dogs were fed exclusively on sugar and distilled water. During the first seven or eight days they were brisk and active, and took their food and drink as usual; but in the course of the second week they began to get thin, although their appetite continued good, and they took daily between six and eight ounces of sugar. The emaciation increased during the third week, and they became feeble, and lost their activity and appetite. At the same time an ulcer formed on each cornea, followed by an escape of the humours of the eye this took place in repeated experiments. The animals still continued to eat three or four ounces of sugar daily; but became at length so feeble as to be incapable of motion, and died on a day varying from the thirty-first to the thirty-fourth. On dissection, their bodies presented all the appearances produced by death from starvation; indeed, dogs will live almost the same length of time without any food at all.

When dogs were fed exclusively on gum, results almost similar to the above ensued. When they were kept on olive-oil and water, all the phenomena produced were the same, except that no ulceration of the cornea took place; the effects were also the same with butter. The experiments of Chossat and Letellier prove the same; and in men, the same is shown by the various diseases to which those who consume but little nitrogenous food are liable, and especially by the affection of the cornea which is observed in Hindus feeding almost exclusively on rice. But it is not only the non-nitrogenous substances, which, taken alone, are insufficient for the maintenance of health. The experiments of the Academies

of France and Amsterdam were equally conclusive that gelatin alone soon ceases to be nutritive.

III. Effect of Too Much Food.

Sometimes the excess of food is so great that it passes through the alimentary canal, and is at once got rid of by increased peristaltic action of the intestines. In other cases, the unabsorbed portions undergo putrefactive changes in the intestines, which are accompanied by the production of gases, such as carbonic acid, carburetted and sulphuretted hydrogen, and a distended condition of the bowels, together with symptoms of indigestion, is the result. An excess of the substances required as food may undergo absorption. It is a well-known fact that numbers of people habitually eat too much, and especially of nitrogenous food. Dogs can digest an immense amount of meat if fed often, and the amount of meat taken by some men would supply not only the nitrogen, but also the carbon which is requisite for an ordinary natural diet. A method of getting rid of an excess of nitrogen is provided by the digestive processes in the duodenum, to be presently described, whereby the excess of the albuminous food is capable of being changed before absorption into nitrogenous crystalline matters easily converted into urea and so easily excreted by the kidneys, affording one variety of what is called lurus consumption; but no doubt after a time the organs, especially the liver upon which the extra amount of the ingested diet throws most of the stress, will yield to the strain of the over-work, and will not reduce the excess of nitrogenous material brought to it into urea, but into other less oxidised products, such as uric acid ; general plethora, and gout being the result. This state of things however, is delayed for a long time, if not altogether obviated, when large meat-eaters take a considerable amount of exercise.

Excess of carbohydrate food produces an accumulation of fat, which may not only be an inconvenience by causing obesity, but may interfere with the proper nutrition of muscles, causing a feebleness of the action of the heart, and other troubles. The accumulation of fat is due to the excess of carbohydrate being stored up by the protoplasm in the form of fat. Starches when taken in great excess are almost certain to give rise to dyspepsia, with acidity and flatulence. Excess of starch or of sugar in the food may, however, be got rid of by the urine in the form of

glycosuria. There is evidently a limit to the absorption of starch and of fat, as, if taken beyond a certain amount, they appear unchanged in the faces.

Requisites of a Normal Diet.

It will have been understood that it is necessary that a normal diet should be made up of various articles, that they should be well cooked, and that they should contain about the same amount of carbon and nitrogen as are got rid of by the excreta. No doubt these desiderata may be satisfied in many ways, and it would be unreasonable to expect that the diet of every adult should be unvarying. The age, sex, strength, and circumstances of each individual must ultimately determine his diet. A dinner of bread and hard cheese with an onion contains all the requisites for a meal, but such diet would be suitable only for those possessing strong digestive powers. It is a well-known fact that the diet of the continental nations differs from that of our own country, and that of cold from that of hot climates, but the same principle underlies them all, viz., the replacement of the loss of the excreta in the most convenient and economical way possible. Without going into detail in the matter, it may be said that anyone in active work requires more nitrogenous matter than one at rest, and that children and women require less than adult men.

The quantity of food for a healthy adult man of average height and weight may be stated in the following table :

weights of dry or solid food practice to be nearly always

The above table contains the required. Such food is found in combined with 50 to 60 per cent. of water, and so the above numbers should be correspondingly increased. The amount of liquids required in addition is about three pints per diem.