Page:Encyclopædia Britannica, Ninth Edition, v. 7.djvu/220

202 202 DIETETICS The attainment of nutritiousness by concentration is of considerable importance to travellers and in military medicine. There are not a few strategists who attribute the success of the Germans in the war of 1870 to the easily carried and easily prepared food supplied to them by the sausage-makers of Berlin. Concentration of viands carried to excess, so as to be likely to affect the health, is usually made manifest by a diminution in the secretion of urine and itscondensed condition; while, on the other hand, if dilution is needlessly great, the action of the kidneys is excessive. Now the urine of young persons is naturally of lower specific gravity, that is, more aqueous, than that of adults. If it is found to equal iu density the excretion of full growth, or if it is observed to be voided but rarely, the meals should be made more bulky, or better still, more frequent, so as not to overload the stomach. An over-concentrated diet often induces costiveness. This should be counteracted by green vegetables and other dilute appetizing dishes, and never by purgative drugs. The habit of taking a considerable quantity and variety of fresh green vegetables has the further advan tage of preventing that tendency to minor develop ments of scurvy which is not uncommonly found in youths nourished mainly on animal food. A softness or friability of the gums is one of the first signs of this. If the mouth bleeds after the application of a tooth brush, the use of fresh vegetables at every meal should be enforced. The young are peculiarly liable to be affected by poisons conveyed in fluids. Their sensitive frames absorb quickly, and quickly turn to evil account such substances, even when diluted to an extent which makes them harmless to adults. The water therefore with which families, and still more with which schools are supplied, should be carefully subjected to analysis. Wherever a trace of lead is found, means should be adopted to remove the source of it ; and organic products should have their origin clearly accounted for, and all possibility of sewage contamination excluded. These precautions are essential, iu spite of the grown-up portion of the household haviug habitually used the water without injury. Fresh milk has long had a bad popular reputation as occasionally conveying fever, and in some parts of Ireland the peasantry can hardly ever be got to take it &quot; raw.&quot; This is quite irrespective of th? state of the cattle which furnish it; no cases of disease thus communicated have ever been traced home to sick cows. It is pro bably always due either to adulteration with dirty water, or to the vessels being washed in that dangerous medium, or to their being exposed to air loaded with elements of contagion. Up to the period of full development the daily use of whie should be allowed only during illness and the express attendance of a medical adviser. Its habitual consumption by healthy children hastens forward the crisis of puberty, checks growth, and habituates them to the artificial sensa tion induced by alcohol. Diet for Bodily Labour. It seems certain that the old theory of Liebig, which attributed the whole of the force exhibited in muscular movements to the oxidation of muscular tissue, is untenable. There is not enough of the material oxidized, that is to say, destroyed and carried away as urea and other nitrogenous excretions, to generate so much force, as measured by the method of Joule. On the other hand, Traube goes too far when he would make out that in the performance of muscular work the metamorphosis of the organized constituents of contractile tissue is not involved, and that non-nitrogenous substances alone are consumed. The prolonged feats of walking performed by the pedestrian Weston in 1876 vastly increased the amounts excreted of those elements of the urine which are derived from the oxidation of muscle and nerve. 1 The urea formed by the destructive assimilation of contractile fibre, and the phosphates whose main source is nervous tissue, were each nearly doubled during and shortly after the extraordinary strain upon those parts of the body. As might be expected, the machinery wears away quicker when it is harder worked, and requires to be repaired immediately by an enhanced quantity of new material, or it will be worn beyond the power of repair. The daily supply, therefore, of digestible nitrogenous food, insat par excellence, must be increased whenever the muscular exercise is increased. In making the recent extension of railways in Sicily, the progress was retarded by the slack work done by the Sicilian navvies compared with that got through by the English gangs. The former took scarcely any meat, preferring to save the wages expended by their comrades in that way. The idea occurred to the contractor of paying the men partly in money and partly in meat ; and the result was a marked increase in the amount of work executed, which was brought nearly up to the British average. A mixed diet, with an increase in the proportionate quantity of meat when extra corporeal exertion is required, is the wholesomest, as well as the most economical, for all sorts of manual labourers. It is absolutely essential that the fleshly machinery for doing work should be continuously replaced by flesh food, as it becomes worn out. Nitrogenous aliment after a few chemical changes replaces the lost muscle which has passed away in the excretions; just as the engineer makes ore into steel and renews the corroded boiler plate or thinned piston. Now, as the renewal of the plate or piston is a &quot; stimulus &quot; to the augmented performances of the engine, so meat is a &quot; stimulus &quot; to augmented muscular action. Taken in a digestible form during exertion, it allows the exertion to be continued longer, with greater ease and less consequent exhaustion. According to the testimony of soldiers experimentally put through forced marches of twenty miles a day, with loads of half a hundredweight each, &quot; meat- extract &quot; bears away the palm from the other reputed stimulants commonly compared with it (viz., rum and coffee). &quot; It does not put a spirit into you for a few miles only, but has a lasting effect ; if I were ordered for continu ous marching, and had my choice, I would certainly take the meat extract,&quot; said an unprejudiced sergeant to Dr Parkes, who was the conductor of the experiments alluded to. 2 When the continuous repair of the muscular machinery is fully secured, the production of heat and force is most readily provided for by vegetable aliment, by reason of the large proportion of carbon which it contains. In assign ing their physiological functions to the several sorts of food, nearly all the business of begetting active force should ap parently be ascribed to the solid hydrocarbons, starch and fat, by their conversion into carbonic acid. It is not necessary to be acquainted with every step of the process, which in the body we confessedly are not, to appreciate the argument. It is clearly important that these elements of diet should be furnished in sufficient quantity and in a digestible form. In additions to diet made in consequence of additional bodily work not only should the stimulus of animal food be attended to, but the bulk of starch and fat in the rations should be augmented even in larger 1 See Dr Pavy on Weston s walk, in Lancet of Dec. 23, 1876. The urea excreted when walking bore to that excreted during rest the rela - tion of 17 to 10, phosphoric acid 19 to 10, lime 15 to 10, &c. 2 On the Issue of a Spirit Ration during the Ashantee Campaign of 1874, by E. A. Parkes, M.D., Professor of Military Hygiene in tho Army Medical School. London, 1875.