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-meat 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 ail sorts of manual laborers.

It is absolutely essential that the fleshy 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 "stimulus" to the augmented performances of the engine, so meat is a "stimulus" 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, "meat extract" bears away the palm from the other reputed stimulants commonly compared with it-viz., rum and coffee. "It does not put a spirit into you for a few miles only, but has a lasting effect. If I were ordered for continuous marching, and had my choice, I would certainly take the meat extract," said an unprejudiced sergeant to Dr. Parkes, who was the conductor of the experiments alluded to.1

1 See Dr..Pavy on Weston's walk, in Lancet of December 23,1876. The urea excreted when walking bore to that excreted during rest the relation of 17 to 10; phosphoric acid, 19 to 10; lime, 15 to 10, etc.

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 assigning their physiological functions to the several sorts of food, nearly all the business of begetting active force should apparently 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 proportion, for these aliments are the most direct contributors of force.2

1 " On the Issue of a Spirit Ration during the Ashantee Campaign of 1874," by E. A. Parkes, M. D., Professor of Military Hygiene in the Army Medical School, London, 1875.

2 This is well illustrated by a remarkable feat performed on the Great Western Railway in the summer of 1872. It was necessary to shift the rails from the broad to the narrow gauge on upward of 500 miles of permanent way within a fortnight. The task was enormous, for the Great Western is one of the few English lines whose rails are held down by bolts screwed into nuts. All these had to be unscrewed, and replaced after removing the heavy rail two feet About 3,000 men were employed, working double time, sometimes from 4 in the morning till 9 at night; and, without one being sick or drunk, they accomplished the work in the prescribed time. The scheme for generating muscular power was this: The men were hutted along the line, so as not to waste their strength by coming and going, and they brought with them bacon, bread, cheese, cocoa, etc., to provide their usual meals at usual times. But they had no beer, nor alcohol in any form. A pound and a half of oatmeal and half a pound of sugar was allowed extra to each man daily, and for every gang of twenty-one a cook was provided. The first thing done in the morning was to breakfast; and then the cook and his caldron started along the line till water was found convenient; a fireplace of stones was built, and the pot boiled. Oatmeal was then sprinkled into it with sugar, and thoroughly well boiled till thin gruel was made. As soon as the "shout for drink " was heard, buckets were filled and carried round, with small pannikins to convey the liquid to the panting mouths. The men liked it exceedingly, and learned by experience the importance of having it well cooked.