FOOD. 129 



food does not depend on its containing either one of the alimentary 

 substances in large quantity, but upon its containing them mingled 

 in the proportions requisite for nutrition. What these proportions are 

 cannot be determined from chemical analysis, nor from any other data 

 than those of observation and experiment. 



Requisite Quantity of Food and of its Different Ingredients. 



The entire quantity of food required per day varies with the circum- 

 stances of the individual, such as the size and weight of the body, the 

 development of the muscular system, the temperature, and especially 

 the amount of physical activity. More food is required, on the aver- 

 age, in cold than in warm weather, more by persons of a muscular than 

 by those of an adipose or phlegmatic constitution, more in a condition 

 of exertion than in one of repose. Even the proportion of different 

 classes of proximate principles required for nutrition varies according 

 to special conditions. When the individual is perfectly healthy, and 

 can supply himself with any kind of nourishment desired, the natural 

 demands of the appetite afford the surest criterion for both the quantity 

 and quality of food to be used. But provision must often be made for 

 supplies to last over a considerable period, as in military or exploring 

 expeditions, or for the inmates of hospitals or asylums where the diet 

 must be regulated to a great extent on a uniform plan. It, therefore, 

 becomes important to know both the quantity and kind of food neces- 

 sary for the support of life. 



The standard adopted for this estimate is that of a healthy adult 

 man, employed in active but not exhausting occupation. The amount 

 requisite will be found to vary in either direction from this standard, 

 according to the circumstances above mentioned. The average require- 

 ments, as given by different authors, do not vary materially from each 

 other in any essential particular. According to our own observations, 

 a man in full health, taking active exercise in the open air, and restricted 

 to a diet of bread, fresh meat, and butter, with water and coffee for 

 drink, consumes the following quantities per day : 



" QUANTITY OF FOOD REQUIRED PER DAY. 



Meat 453 grammes. 



Bread , 540 



Butter or fat 100 



Water 1,530 



This represents the daily quantity of food and the proportions of its 

 different kinds, when composed of such materials as are most nutritious, 

 and of the most uniform composition. For the continued maintenance 

 of health and strength in a working- condition, other articles, such as 

 fresh vegetables, sugar, milk, fruit, etc., should be mingled with the 

 above, in a variety of proportions ; but there is no doubt that bread 

 and fresh meat, with a certain quantity of fat, will prove sufficient for 

 the wants of the system, for a longer time than any other articles of 

 food. 



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