186 PHYSIOLOGICAL CHEMISTRY 



Various forms of temporary glycosuria are known. Thus, 

 after excessive exercise, during great agitation or mental strain 

 such as often is experienced by students taking a difficult ex- 

 amination (emotional glycosuria), or after taking excessive 

 amount of simple carbohydrates (alimentary glycosuria) sugar 

 may appear in the urine. In the case of the first two conditions, 

 the glycosuria is believed to depend on a production of adren- 

 aline, which is known to be secreted at times of great exertion or 

 emotional stress, a logical process, since at such times the mus- 

 cles are apt to need an increased supply of fuel for use in pos- 

 sible pursuit, flight, or combat. 



An important phase of carbohydrate metabolism is concerned 

 with the ultimate fate of the glucose which is burned as fuel. 

 How and where does the burning or oxidizing take place, and 

 how is it controlled? There is still much uncertain ground in 

 this field, though much progress has been made. Various 

 methods have been employed to throw light on the problem. In- 

 teresting results have developed from a study of the Respiratory 

 Quotient. This term is used for the ratio between the amount of 

 carbon dioxide excreted in the respired air, and the amount of 



CO 

 oxygen consumed, and is indicated as ^ 2 . If glucose is oxidized 



^2 



to C0 2 and water a certain amount of oxygen is consumed. 

 C 6 H 12 6 +6 2 ^6 C0 2 +6 H 2 0. 



For every molecule of C0 2 produced, one molecule of 2 is used 

 up. There already is, enough in the carbohydrate to take care 

 of the hydrogen present. Thus the volume of 2 consumed 



CO 

 equals the volume of C0 2 produced, and T\ = 1. This will 



U 2 



be true in the body as well as elsewhere provided the oxidation 

 of the carbohydrate to C0 2 and H 2 is complete. If a fatty 

 acid is burned in the same way, the respiratory quotient is less 

 than one. It does not contain sufficient oxygen to take care of 



