Succulent vegetables. The various succu lent roots, fruits, and herbs made use of as articles of food, possess a cornposition which, though different in each particular instance, may still be comprehended in one general description. With little protein or starch, they include a variable quantity of sugar, pectin, gum, organic acids, and salts ; united with what is alssays a large proportion of water.
Thus in the class of roots* represented by turnips, carrots, and beet-root, the quantity of albumen is not inconsiderable ; ranging from 1 to 3 per cent.+ : and the pectin itself, ( (1,2 H 0,0 ) is in much more consi derable quantity. The organic acids of these and the various fruits are too numerous to specify ; but the malic, which is also found in the potato, is one of the most frequent. The fruits contain still less protein and starch than the above roots. The young shoots and leaves of the several varieties of cabbag,e include starch, and some albumen, as well as sugar. The fixed salts of these various esculent vegetables are little known. In fruits their quantity is small. But in the green vegetables it is larger. And, finally, in the pectinous roots, they form about 11 per cent. of ash ; in which Boussingault has found most of the ordinary acids and bases, with propor tions somewhat approaching those seen in the potato ; save that lime and soda are in creased, while phosphoric acid is diminished.
The nutritive value of these vegetable sub stances is therefore very considerable. Defi cient as most of them are in the proteinous principle, they are of course unsuited for the maintenance of nutrition without the admix ture of other azotized substances. The precise way in which their pectin is applied to the uses of the organism cannot at present be explained. But its composition is so far akin to that of the gum and sugar which accompany it, that we may conjecture it subserves pur poses similar to those accomplished by these hydrates of carbon. The salts of such vegetables replace those lost by the body ; and, although deficient in phosphates, seem to form what is, in most other respects, a tolerable compen sation for the waste of excretion. Finally, their organic acids disappear in the blood, in which they probably undergo an oxidation that ultimately converts them into carbonic acid and water.
With respect to the two latter consti tuents, namely, salts and acids it is im portant for us to recollect, that there are many phenomena of health and disease hich teach us, far better than our pre sent knowledge of physiological chemistry, what is the true value to the organism of such compounds. The incontrollable
longing of Man after variety of diet, appears to find vent chiefly in the cultivation and consumption of esculent vegetables of this class. While scurvy, and other dangerous diseases of the same kind, which are still too prevalent among us, may serve to advise us that, within certain limits, this instinctive taste represents a bodily want, the satisfying of which is not so much a concession to the cravings of luxury, as a payment of the just claims of health.
The sea.sonings generally added to food are rarely alimentary in the strict sense of this svord.
Chloride of sodium, or common salt, is, however, a marked exception to this rule ; being habitually taken by most nations, and eagerly sought after by many animals, both wild and domesticated. Its use in reference to digestion may be presumed to depend chiefly on its relationto the acid*of the gastric juice. But the alleged results of its complete withdrawal from the food of criminals, are such as to suggest an antiseptic action of this salt on the contents of the stomach, even independent of that exerted by the gastric juice itself And the office it subserves with reference to nutrition generally, appears to be a still more obscure one. Its habitual ingestion seems to facilitate the process of fattening, as well as to increase the amount of excretion. The large constituent which it forms in the ash of the blood and of most of the tissues, probably has some reference to all these details.
The other seasonings chiefly made use of in civilized life may be divided into two classes; acids, and acrid substances. The former consist of various organic acids; espe cially acetic acid or vinegar, and lemon juice. These seem to act mainly by stimu lating the stomach ; perhaps increasing the acidity, and with this the solvent energy, of the gastric juice. The various acrid sub stances mustard, pepper, capsicum, garlic, &c. are also supposed to stirnulate the secretion of this fluid, by exciting a violent determination of blood to the mucous mem brane of the stomach. Many of them are irritant poisons, when taken in undue quantity.