406 



PHYSIOLOGICAL CHEMISTRY. 



Since then many similar observations have been made which 

 show pretty clearly that when fats or carbohydrates are abund- 

 ant in the food there is no excessive destruction of protein in 

 the performance of ordinary work. With the ingestion of a 

 small amount of protein it is easy to cover the normal metab- 

 olism. But the case is different when the work is hard. 

 Here, even with abundant food and plenty of protein, there 

 appears to be some loss of nitrogen by the body. In other 

 words, more tissue is broken down than is formed new. This 

 is brought out clearly in the observations of Atwater on the 

 work done by bicyclers in a six-day race some years ago, in 

 which the food consumed and nitrogen eliminated were care- 

 fully watched. The following table gives a summary of the 

 most important observations, with the energy in large calories : 



Riders A and B rode through six days. C rode three days. 

 The energy metabolized does not include that from body fat, 

 which may have been considerable. 



DIETARIES. 



The question of the proper amount of food and the charac- 

 ter of the food for different kinds of work has been very 

 thoroughly studied in the past few years and a large number 

 of observations on individuals, families and communities of 

 soldiers, prisoners and paupers have been collected. The diet 

 in some cases is known to be sufficient, in others insufficient. 

 From present experience it is possible to say of many dietaries 

 that they are excessive, and probably objectionable in conse- 



