TOPOGRAPHY OF ABDOMINAL ORGANS.
(Plates XII., XIII., XIV.) To make still clearer the position of the vari ous organs in the cavity of the belly, a series of plates has been prepared. Each plate repre sents the situation of one or more organs, the others being at the moment neglected. For in stance, Plate XII. represents the kind of draw ing that might be produced if a man were to ask an anatomist to trace in chalk on his skin an outline showing the whereabouts of the stomach and large bowel. These plates are self explanatory, but the interested reader would derive some advantage by referring at this point to Plate XII. and its description, as well as to Plates XIII. and XIV.
It is not intended at this place to discuss all that is included under the general heading Food. That is delayed to the part of the work devoted to HYGIENE, where information will be suppose a person to be suffering from pain or swelling at a limited part of the belly, by refer ring to the list some idea would be gained of the organ or portion of organ that was probably affected.
given about the various kinds of food-stuffs ' of a more detailed character. Only what is necessary for the understanding of the pro cess and purpose of digestion will be considered mre.
The Necessity for Food. — A healthy man, doing his ordinary daily work, may be :ompared to a steam - engine in thorough working order. As an engine uses up fuel Ind water for the purpose of obtaining from them the energy necessary to perform its work, 50 a man consumes certain substances in order to obtain from them the energy necessary for his life and activity, and all these substances he obtains from the blood. In short, a man by the daily work of his body, whether that work implies merely the movements of heart and chest, the maintenance of the heat of the body, and so on, just what is necessary for life, or implies besides manual or mental labour—a moan by the daily work of his life consumes cer tain parts of his body. Waste goes on within his body. Suppose the waste were allowed to continue, no effort being made to supply the place of what had been consumed, the man would continue to live and work at the expense of his own body. This could not long be en
dured without danger. The waste must, there fore, be repaired, and food is the means by which this is accomplished. Let us see now what is the nature of the waste. An ordi narily healthy man passes out of his bowels daily, on an average, 5i oz. of material, a large proportion of which—not less than 75 per cent indeed—may be considered water, by the kid neys, 56 oz., 96 per cent of which is water, by the skin, in the shape of sweat, a variable quan tity, 23 oz. or thereby, of which 99 per cent is water, and by the lungs 34 oz., of which 10 oz. are water and the remainder carbonic acid gas. Therefore, setting aside for the moment the 25 per cent of the solid matter removed from the bowels, which will be mainly indigestible or undigested remains of the food—setting that aside, the main bulk of what a man passes out of his body daily consists of water, carbonic acid gas, and certain solid matters contained in solution in the urine, sweat, &c. Now, the chief of these solid matters is a substance found in the urine called urea. Urea is made up of the four elements carbon, hydrogen, oxygen, and nitrogen. Water contains only two ele ments, hydrogen and oxygen, and carbonic acid also only two, carbon and oxygen. It appears, therefore, that what a man casts out of his body daily consists essentially of four elements, carbon, hydrogen, oxygen, and nitrogen. Now these four elements cast out of the body in the shape mainly of water, carbonic acid gas, and urea, represent the consumption that has been going on in the body to produce the energy necessary for the man's life, even as the smoke, ashes, and steam represent the consumption of fuel and water going on in the steam-engine. It is, consequently, evident that if one could restore to the body daily a quantity of those four elements similar to that cast out one would be able to make up for the waste that had been produced. The purpose of food, then, is to restore an amount of the four elements equal to that used up, to repair the waste.