It is pretty well known what the constituents of the animal organism are, and what elements of nutrition are required in the food for the sustenance of the animal. Of these primal elements--some twelve or fifteen in number--it is found that, practically, when foods combined contain two of them in proper proportion, the rest are generally present in sufficient quantity. These two are CARBON and NITROGEN, and the foods containing them in relatively large proportion are respectively called _carbonaceous_ and _nitrogenous_. All foods contain these elements in greater or less proportion. The proper proportion for feeding is found to be about _one_ of nitrogen to _five_ or _six_ of carbon. If the temperature of the weather is low, the proportion of carbon may be raised to eight, and even ten, where little exercise is had--as, for instance, milch cows standing in a cold stable. But, in hot weather, when cows are giving milk, the carbon may be reduced to four and even three--that is, so that there shall be one part of nitrogen to three or four parts of carbon. The carbon is heat and fat producing, and some class it as motor producing, but we think this is a mistake, save so far as heat is essential to motion. We think nitrogen is motor producing as well as muscle producing--or, in other words, that the element which produces the organs of motion also fills them with energy, for the exercise of which heat is essential. We cannot have motion, or even life, much below the normal temperature of about 98 degrees Fahrenheit. At all events, it is found necessary to feed nitrogenous food to all animals that are working hard, to supply the waste of muscle--and we think also to replace the expended energy. Dr. J. Milner Fothergill, in his work on the "Maintenance of Health," published by G.P. Putnam's Sons, says: "The effect of the nitrogen upon the brain is to _evolve nerve force freely_, and this rules and regulates the actual force which takes its origin in the respiratory foods consumed. These respiratory foods furnish the force itself, but the nitrogenized foods furnish the manifesters of force." It appears to us that the nerve force, which he says is evolved, is all there is of it, save the requisite conditions afforded by heat. Dr. Houghton says: "The hunted deer will outrun the leopard in a fair open chase, because the force supplied to its muscles by vegetable food is capable of being given out continuously for a long period of time; but in a sudden rush at a near distance, the leopard will infallibly overtake the deer, because its flesh food stores up in the blood a reserve of force capable of being given out instantaneously in the form of exceedingly swift muscular action." Dr. Fothergill goes on to say: "Nitrogen is the essential factor in all explosive compounds, from gunpowder to nerve force. It endows the consumer of it with energy and enables him to discharge his force quickly and rapidly." Again, he says of the