LECTURE XXVIII. 



GENERAL METABOLISM. 



II. 



THE human and animal organism requires for the maintenance of its 

 bodily condition and for the exercise of its functions a perfectly definite 

 amount of nutriment. The nutritional requirement depends, naturally, 

 upon various external conditions. Unquestionably individual peculiari- 

 ties also come into play here, at least to some extent. One very important 

 factor is the amount of work to be performed. It is also self-evident that 

 the large amount of new tissue which is being formed in the growing 

 organism also influences the amount of food required. 



There are a number of different ways for getting an idea of the amount 

 of food required under definite conditions. For one thing we can ascertain 

 the diet chosen by different people of various callings, and estimate from 

 'its composition the calorific value, and use this as a basis. If this is done 

 with a number of different individuals for each class, then we shall obtain 

 very useful average values. A single observation does not give a reliable 

 indication of the food requirement. Certain circumstances, such as the 

 nature of the food chosen, its utilization, especially in individual cases, 

 lessen the value of the calculated amount of calories from a single observa- 

 tion. The greater the amount of material worked over, and the more 

 uniform the external conditions are, the less influence will be exerted by 

 individual peculiarities. It is perfectly clear that all such estimations 

 will involve more or less error, and at best we can only arrive at approxi- 

 mations. 



It is usually not possible to determine in such investigations the extent to 

 which the food material is utilized. Such computations must be based upon 

 exact experiments on metabolism. Nevertheless, such observations have 

 great value from a hygienic-sociological standpoint. The physiology of 

 metabolism has become epoch-making in this direction. By means of it, 

 attention has been called to the altogether insufficient nourishment of 

 certain classes. It is perfectly clear that a permanent underfeeding and 

 too low standard of life must eventually tend to weaken the individual. 

 The resistance towards injurious external influences, towards infectious 

 diseases, etc., becomes lessened, morbidity and mortality increase, the 

 growth of children becomes retarded, the number of able-bodied men for 



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