What is an important use of the first class of proximates?
What may lungs be called?
Explain the production of heat during decomposition.
Why is the heat produced by decay not perceptible?
Apart from the relations between the proximate principles of plants, and those of animals, there exists an important relation between their ashy or inorganic parts; and, food in order to satisfy the demands of animal life, must contain the mineral matter required for the purposes of that life. Take bones for instance. If phosphate of lime is not always supplied in sufficient quantities by food, animals are prevented from the formation of healthy bones. This is particularly to be noticed in teeth. Where food is deficient of phosphate of lime, we see poor teeth as a result. Some physicians have supposed that one of the causes of consumption is the deficiency of phosphate of lime in food.
Why is the heat produced by combustion apparent?
Explain the production of heat in the lungs of animals?
Why does exercise augment the animal heat?
Under what circumstances is the animal's own fat used in the production of heat?
The first class of proximates (starch, sugar, gum, etc.), perform an important office in the animal economy aside from their use in making fat. They constitute the fuel which supplies the animal's fire, and gives him his heat. The lungs of men and other animals may be called delicate stoves, which supply the whole body with heat. But let us explain this matter more fully. If wood, starch, gum, or sugar, be burned in a stove, they produce heat. These substances consist, as will be recollected, of carbon, hydrogen, and oxygen, and when they are destroyed in any way (provided they be exposed to the atmosphere), the hydrogen and oxygen unite and form water, and the carbon unites with the oxygen of the air and forms carbonic acid, as was explained in a preceding chapter. This process is always accompanied by the liberation of heat, and the intensity of this heat depends on the time occupied in its production. In the case of decay, the chemical changes take place so slowly that the heat, being conducted away as soon as formed, is not perceptible to our senses. In combustion (or burning) the same changes take place with much greater rapidity, and the same amount of heat being concentrated, or brought out in a far shorter time, it becomes intense, and therefore apparent. In the lungs of animals the same law holds true. The blood contains matters belonging to this carbonaceous class, and they undergo in the lungs the changes which have been described under the head of combustion and decay. Their hydrogen and oxygen unite, and form the moisture of the breath, while their carbon is combined with the oxygen of the air drawn into the lungs, and is thrown out as carbonic acid. The same consequence—heat—results in this, as in the other cases, and this heat is produced with sufficient rapidity for the animal necessities. When an animal exercises violently, his blood circulates with increased rapidity, thus carrying carbon more rapidly to the lungs. The breath also becomes quicker, thus supplying increased quantities of oxygen. In this way the decomposition becomes more rapid, and the animal is heated in proportion.