ENERGY RELATIONSHIPS. 329 



bacteria, the residue of digestive juices, and the debris of the epithelial 

 lining of the intestinal tract. It is the common custom to analyze fecal 

 material and to consider the nitrogen obtained as a measure of the 

 unabsorbed protein, the fat as unabsorbed fat, and the carbohydrate, 

 although existing in small amounts, as unabsorbed carbohydrates. 

 This is fundamentally wrong, although the method for determining the 

 digestibility of food has been based upon these false premises practi- 

 cally ever since the introduction of food analysis. It can be seen that 

 an absorption of 95 per cent on this basis would, when properly inter- 

 preted, mean an actual energy absorption of nearly 98 per cent; hence 

 the advocates of excessive mastication must attempt to increase an 

 absorption which is already 98 per cent of the total amount. This is 

 obviously impossible and physiologically unsound. If we further con- 

 sider the extra energy required for excessive mastication, it is more 

 than probable that such slight increase in absorption as may possibly 

 occur with an excessive comminution of food materials by prolonged 

 chewing may be considerably more than offset by the additional con- 

 sumption of energy required for mastication. 



In the experiments on drinking liquids, such as water which is with- 

 out nutritive qualities, beef tea which has a measurable amount of 

 the stimulating extractives (creatine and allied compounds), and coffee 

 which contains a slight amount of extractives and of caffein (a heart 

 stimulant), the picture is again not uniformly clear. Sufficient experi- 

 mental evidence has been accumulated, however, to state positively 

 that the drinking of large amounts of water results in an actual increase 

 in the total production. Beef tea, taken either hot or cold, likewise 

 slightly increases the metabolism. Coffee produces a similar slight 

 increment. While a logical explanation of the increase in metabolism 

 due to coffee and beef tea might be found in their content of stimulating 

 materials, such as caffein and creatine, it is difficult to explain the 

 increase due to water on this basis, and it is not impossible, even in the 

 absence of positive evidence, that we have to deal here with an internal 

 mechanical process which may be directly associated with the secre- 

 tion of the normally occurring large amounts of urine following exces- 

 sive liquid ingestion. 



In a final consideration of the results of drinking liquids which show, 

 as a rule, a relatively small increase in metabolism due to this factor, we 

 must again state that the experimental technique was by no means 

 perfect at that period of the research, and that the defects in the base- 

 line frequently vitiated many of the results. As was clearly brought 

 out in the discussion of the basal metabolism, such variations have 

 considerable significance when the basal values are used for compar- 

 ison with values obtained in subsequent periods in which only small 

 increments are found; it is thus especially important to secure accu- 

 rate basal values for such experiments. Accordingly, in studying the 



