Human physiology / by William Furneaux.

  • Furneaux, William S.
Date:
1909
Catalogue details

Licence: In copyright

Credit: Human physiology / by William Furneaux. Source: Wellcome Collection.

    94/270 (page 82)
    b2 By means of the skin we part with waic?\ a small quantity of mineral salts, and a little carbonic acid gas. The kidneys are the source of a considerable loss of water, and a very large quantity of urea. The loss by the skin varies very considerably. The exu- dation through its pores is commonly known as perspiration or sweat. In hot weather, or during violent exercise, we perspire very freely ; so much so that the skin becomes covered with globules of water, containing carbonic acid gas and urea in solution. But in cool weather, and during rest or the taking of gentle exercise, the liquid exuded evaporates into the air as fast as it reaches the surface, and consequently the perspiration is insensible. From the above we learn how the four chief elements of the body—oxygen, carbon, hydrogen, and nitrogen, are lost. The loss of hydrogen and oxygen in the form of water is very variable, and is replaced largely by the water contained in our foods and drinks. The loss of carbon and nitrogen is repaired by the use of organic food-substances, and amounts to an average of 4,500 grains of carbon and 300 grains of nitrogen daily in an adult person, taking moderate exercise. The high temperature of the body (98-4“ F.) is produced and maintained by chemical action. This action is chiefly oxidation, very closely resembling that which takes place when a candle burns (see page 78). The materials to be oxidised are supplied through our foods. A constant supply of oxygen gas is also obtained by the blood as it circulates through the lungs; and we may regard the carbonic acid gas given off as the product of the continuous oxidation of carbon in the body. If we cease to take food for any considerable time the body gradually wastes away, and in a few days a marked change is pro- duced in the general appearance. The discharge of waste matter by means of the lungs, skin, and kidneys still continues, and every muscular exercise adds to it. As no food is being taken, the temperature of the body is maintained by the oxidation and consequent wasting away of the tissues. After a few days the temperature decreases, till, at about the ninth or tenth day, the body has lost about forty per cent, of its weight, and is reduced to a temperature of about 70° F, when death from starvation puts an end to the painful existence. Before considering the manner in which the waste of the body may be most advantageously repaired, it will be necessary to learn the nature of the various food-substances of which we make use. Food-substances may be divided into organic and inorganic.