KEEPING WELL 417
equipment for the recurring struggles and labors which each day may bring.
It would seem probable, a priori, that the aged, with enfeebled powers of mind and body, would require more sleep than those whose powers are active and vigorous. This may be so in many, perhaps in the majority of instances. A lethargic, inactive condition in the aged is common, from which the transition to sleep is easy and natural. It very often happens, however, that aged people do not require so many hours of continuous sleep as those who are younger, three or four or five hours at night sufficing, with perhaps an hour or two during the day. It would be an interesting subject to speculate about, and could be explained on physiological grounds.
Equal in importance with almost any of the questions which have been discussed in connection with personal hygiene is that of diet. The question for civilized man not only is, How much shall I eat? but, What shall I eat? and physiology and chemistry have been giving very exhaustive answers during many years of investigation. We are not considering the man who eats everything within his reach which is eatable, or which he assumes to be eatable, but the one who has a certain amount of intelligence, and who realizes that some articles of diet may be more useful to him than others.
It seems hardly necessary to say that infants and young children are not provided with organs to digest the same or the same quantity of food as adults, and when they are fed from the common family table, as is often the case among the poor and ignorant, it is not strange that only the fittest survive. It would be startling if the facts were known as to the thousands of children who are annually killed by improper food. Food for the young is, therefore, not necessarily appropriate for the mature, and vice versa.
The fundamental object of food is the production of heat and vital force, and it is quite analogous to the production of heat and force in an engine by means of fuel. Food is not required to the same extent in summer as in winter. In a cold