The body is composed of a vast number of cells varying according to the tissue or organ in which they are found. The characteristic of all living matter is that it constantly reproduces itself. Cells perform their appointed work, wear out, and must be replaced by new ones or derangements follow.
The new cells constantly being formed, increase in size and in so doing push the worn-out, dying, and dead cells out of the way. The process of building and eliminating continues within the body and on its surface every instant of life.
An idea of the number of dead cells constantly being thrown off from every part of the body may be gained by noticing the amount of dead skin cast off. The fine scales of “scarf” or “dead” skin, which we easily rub off in a friction bath, are composed of these dead cells which have been crowded out by the hosts of vital cells constantly forming beneath. The process is the same in every tissue and organ. The dead or worn-out matter within the body is burned by oxygen and put in condition to be carried by the blood to the organs of elimination, the kidneys, intestines, lungs, and skin.
Much waste is eliminated in liquid form through the sweat glands. It is said that stokers throw off four pounds of water and waste a day through the skin.
In the growing child the process of building and of eliminating is active and rapid. In the youth it is less rapid, in the adult still less, but unless the process is kept active, stagnation and death ensue.
Daily exercise is necessary to keep up the body activities; yet very few take the trouble to secure daily a complete, thorough circulation of blood, especially through the vital organs and the deeper tissues. Perfect circulation is the key-note of health.
Activity of any kind necessitates the expenditure of energy. The process is a chemical one and in all chemical processes heat is necessary to cause the decomposition of elements and their recomposition into different substances.
Heat in its turn has two functions. It enables the chemical changes to be carried on which fit the food for the use of the various tissues, and it burns to an ash the worn-out products of the body’s activity, fitting them for elimination.
It keeps the tissues flexible and the secretions fluid; coagulation takes place when the secretions become cold.
As previously stated, food in the body, then, is needed for two purposes: