The next question which presents itself is, What is the proper food of man? In answering it, we must begin by making distinctions, otherwise we shall, in the very outset, fall into error.
On examining the structure of the human body at different ages, and in different individuals, remarkable differences are observable in the relative proportions of the elements or tissues of which it is composed. In one, the muscular system predominates, and the body is remarkable for a compactness of fibre indicative at once of strength and activity. In another, the lymphatic system is the most conspicuously developed, and its features are easily recognised by the full, soft, and rounded form, and languid action, which generally accompany it. In a third, the thin and sharp outline, irregular and vivacious activity, and great susceptibility of impressions, betoken the predominance of the nervous over all the other functions; while, in a fourth, the florid complexion, expanded chest, and general vivacity of disposition, as clearly point out the superior development and energy of the vascular system. Such are the four principal constitutions, long familiarly known under the names of the bilious, the lymphatic, the nervous, and the sanguine temperaments. Very frequently the habit of body indicates a mixture of two or more of these temperaments, in which case the results of course are modified according to the proportions in which they are combined.
The elementary textures being thus differently proportioned in different individuals, it follows that the aliment best suited for the support and repair of one is not always so for the others; in other words, a distinct modification of diet ought to be adopted for every marked variety of constitution, because a direct relation ought always to subsist between the qualities of the food and the nature of the system which it is intended to nourish. Thus, the highly concentrated and stimulating food which is found necessary for the proper sustenance of the trained pugilist or sportsman, whose muscular frame is in high development and constant exercise, would prove far too exciting to the slender and irritable constitution of a person whose characteristic feature is the predominant activity of the brain and nervous system. And, in like manner, the generous and stimulating diet which suffices merely to rouse a phlegmatic organization to ordinary energy, would prove by far too nutritive for a person of a florid and sanguine temperament, whose predisposition is already towards inordinate activity.
The necessity of adapting the diet and regimen to the individual constitution and mode of life, becomes so obvious to reason, when thus plainly stated, as to excite surprise that it should ever have been neglected. But, strange to say, although the ancient writers attached much importance to the subject, the relation between diet and constitution, as a practical consideration, has of late been so entirely overlooked, and sound physiological principle has been so little consulted in the proper adaptation of the one to the other, that we are at this moment in possession of very little information of any value regarding it, and a long time must elapse before more can be supplied. My own observations have not been extensive or accurate enough to enable me to supply any considerable results; and the following imperfect remarks are subjoined rather in the hope of exciting inquiry than of satisfying the curiosity of the reader.
Where the constitution is of a mixed nature, or a compound of two or more of the temperaments already described, a diet composed of animal and vegetable aliment in nearly equal proportions is under ordinary circumstances the best. But where any one temperament predominates, the diet ought to be modified accordingly. Where, for example, the sanguine constitution prevails, characterized by a florid complexion, great activity, strong action of the heart and bloodvessels, and a consequent liability to diseases of excitement and inflammation, the food ought to be habitually of a kind calculated rather to soothe than to stimulate. Red-meat, spices, wines, and fermented liquors ought to be used sparingly; and the principal support to be derived from refreshing soups, fish, mucilaginous vegetables, acidulous fruits, and diluting drinks. In the case of lymphatic persons, on the other hand, where the circulation is weak and slow, and all the functions are feeble, the system is benefited by the stimulus of a larger proportion of animal food, especially red-meat and game; while vegetables, soups, and fluids of all kinds prove relaxing and hurtful. Aromatics and spices, however, are useful, as is also wine in moderation, and conjoined with adequate exercise.
If, again, the individual presents a highly nervous temperament, characterized by delicacy, unusual sensibility to impressions, and great excitability, without proportionate strength, such as is often seen in females and in men of genius, care ought to be taken not to make use of a heating or stimulating regimen. White-meat, such as fish and fowl, are more suitable than the kinds in ordinary use. Spices are also hurtful, but farinaceous and mucilaginous aliments and ripe fruits are generally admissible—always supposing that moderation in quantity is attended to, and that the mode of life is, in other respects, regular and rational.
Where the dark energetic bilious temperament predominates, and much bodily activity in the open air is enjoyed, more latitude in the choice of food is admissible than in any other constitution. If, however, much and continued exertion is required, a full supply of animal food becomes indispensable for the due support of the system, and the strength cannot be adequately supported on vegetables alone. In such circumstances a moderate allowance of wine or other stimulus is borne with less detriment, if not with more advantage, than where the temperament is essentially nervous.
On this subject, however, there is still so much need for inquiry, that I shall not enter farther into details, but urge the reader to make observations for himself.
There is no kind of alimentary substance of which it can be said absolutely that it is always proper for the sustenance of man. To be serviceable, the food must be adapted to the age, constitution, state of health, and mode of life, of the individual, and to the climate and season of the year. The same diet which, administered to an adult, is healthful and nutritious, may prove irritating and injurious to a child; and, in like manner, the stimulating animal diet which in winter is highly grateful to the system of a hard-working unexciteable labourer, may prove utterly destructive of health when indulged in during summer by an inactive and exciteable female. It becomes, therefore, an object of deep interest to determine the principal causes and states of the system which render modifications of diet necessary.