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♦ KNOWLEDGE 



[May 25, 1883. 



"OUR BODIES:" 



SHORT PAPERS ON PHYSIOLOGY. 



By Dr. Andrew Wilson, F.R.S.E., etc. 



No. XII.— THE BODY'S INCOME AND EXPENDITURE. 



IN the course of our previous studies we liave seen tliat 

 the work of the l)0cly is perpetually associated with 

 waste. Work and waste bear, in fact, a very well de6ned 

 relation to each other ; and of necessity, the function of 

 nourishment, wliereby repair of this waste is effected, must 

 in turn lelatc itself to lioth processes. Work is impossible 

 without the energy (or power of performing it) wc derive 

 from our food, and the bodily waste is merely one indication 

 of the extent to which that energy has been applied in 

 carrying out the acts of life. A human body, as 

 the result of its work, then, is perpetually breaking 

 down, in a chemical sense, into various waste products. 

 Of these products so mucli heat may be regarded as waste 

 matter, seeing that it is given off from the body, and is 

 thus lost to it. Water forms a second product of extreme 

 importance, as also does, thirdly, the gas named carbonic, 

 acid. A fourth kind of waste is represented by the sub- 

 stance known as urea ; and, fifthly, we can detect ammonia 

 amongst the waste materials of our frames. To these we 

 may add organic matters of various kinds, consisting of 

 the actual worn-out cells and particles of the body ; and 

 minerals, whereof a considerable quantity is excreted or 

 given off by the skin and kidneys especially. 



The work of excreting or removing these waste matters 

 from the blood, into which they have been poured as the 

 result of the tissue-waste, falls chiefly upon the lungs, 

 skin, and kidneiis. These organs form, in fact, a kind of 

 physiological trio, engaged in the same kind of work, and 

 capable of mutually aiding each other in its performance. 

 The same products are excreted by all three organs, but in 

 different proportions. The practical benefit of this know- 

 ledge is seen in the treatment of many diseases. For when 

 the lungs are disordered in any way, the physician can 

 compel the skin and kidneys to take up so much of the 

 lung's work, by giving medicines which stimulate the skin 

 and kidneys respectively. When the kidneys similarly 

 suffer disorder, skin and lungs come to their assistance. 

 Tlie mere fact that skin and lungs co-operate to perfectly 

 and invariably during exercise is sufficient to impress upon 

 us the close interdependence wliich exists between these 

 organs. 



When we endeavour to sum up the income and expendi- 

 ture of the body in a kind of physiological balance-sheet, 

 we are met by the consideration that whilst the work of 

 repair, or the facts of bodily'income, are plainly enough to 

 be discerned, the sources of loss or expenditure are not so 

 readily noted. We know that food — solid and liquid — is 

 converted into our own substance, and that the oxygen of 

 the air also forms part of our dietary, since it is necessary 

 for the maintenance of heat, and for other vital purposes. 

 But the sources of loss are not so apparent as the means 

 and ways of gain ; hence we must firstly see where and 

 Jiow the bodily income is spent. A little consideration 

 will show us that there must be a considerable amount 

 of loss incurred through the action of what may be 

 called the ordinary "wear and tear" of life. All 

 the organs and tissues must wear and lose their 

 substance in the discharge of their duties. In such an 

 organ as the stomacii, daily engaged in the important 

 work of digestion, or the liver, which is perpetuallv en- 

 gaged in its labour of manufacturing bile, there must be 

 constant loss of substance. Again, there is actual waste of 

 muscular substance in every movement of life, from the 



winking of an eyelid, or tlie .stroke of the heart, to the 

 blacksmith's energetic labours, hammer on anvil. Much 

 of the bodily waste (water, heat, carbonic acid, etc.,) must 

 therefore arisr; from this source. A second source of 

 waste is that incurred in the production of heat 

 and of movement in our bodies. We are perpetually losing 

 and giving off heat, yet the normal temperature of our 

 bodies (about 100° Fahr.) requires to be maintained. Such 

 an amount of heat cannot be generated without expenditure 

 of force, or without the presence of asli, so to speak, which 

 ash makes its appearance in the form of certain of the 

 waste products already mentioned. As regards bodily 

 iiiotio7i, we have already noted the immense expenditure 

 which muscular action entails upon us. 



Other and more subtle forms of waste make demands 

 upon our stores of energy, and necessitate bodily wear and 

 tear as an equivalent. The thoughts that originate in the 

 brain, the expression of nerve-force to which they give rise, 

 its conveyance by the nerves, are, each and all, so many 

 sources of waste and bodily expenditure. Even grovth 

 itself, the digestion of food, the propulsion of blood through 

 the body, and all other processes of nourishment, necessitate 

 an outlay of the store of strength we possess. It is thus 

 perfectly true, in one sense, that life is a process in which 

 we burn the candle at both ends. The very acts whereby 

 we build up our frames anew, and nourish our bodies, 

 whilst repairing these frames, at the same time draw from 

 them the strength and energy we owe to previous acts of 

 nourishment. 



Summing up the sources of income of our bodies, we 

 may discover, firstly, that in solid food, mater, and oxygen 

 we may be said to place our physiological trust. An adult 

 consumes every day about 8,000 grains of solids, about 

 .3.5,000 grains weight of water, and about 13,000 grains 

 weight of oxygen. Nearly 8^ lb. of matter, calculating 

 roughly, represent the daily income. Daily expenditure 

 practically shows a similar amount, for supposing growth 

 has ceased, then income and loss will, in health, be as 

 nearly as may be adjusted ; and if our means of 

 research were more delicate, they would probably 

 be found, in health, exactly to correspond. From 

 the lungs we give off, per day, carbonic acid gas, 

 water, and organic matters equal to 2(1,000 grains. The 

 skin gets rid, in the same time, of nearly 12,000 grains 

 weight of water, minerals, gases, etc. The kidneys excrete 

 about 24,000 grains of waste (water, urea, minerals, etc.), 

 and from the intestine the digestive waste given off may 

 be estimated at aliout 2,800 grains weight. It follows that 

 with about 8^ lbs. of material income, and the same amount 

 of material expenditure, a man will deal with about 

 .3,000 lbs. weight of matter per annum ; and we can- 

 not regard the amount as excessive, if we consider, 

 even for a moment, the immense amount of work 

 which his body performs upon that material, and the 

 results of its conversion into bodily power. It has been 

 calculated, indeed, that the daily force expended by an 

 adult in maintaining his temperature, or heat, in the work 

 of heart, lungs, etc., and in his muscular acts, may be set 

 down at 3,400 foot-tons. In other words, the daily life of 

 man, summed up in one huge lift, would be capable of 

 raising 3,400 tons one foot high. 



An American paper gives the following : — The United 

 States burns about 322,000,000 dols. worth of wood every 

 year. Railroads burn over 5,000,000 dols. worth. Brick 

 and tile factories burn 4,000,000 dols. Jlining operations 

 consume, as fuel, 3,.500,000 dols. worth. Steamboats 

 burn about 2,000,000 dols. worth. 



