THE METABOLISM OF THE CARBOHYDRATES 675 



level of the blood and therefore a tendency to diabetes. There have 

 recently been collected several facts which lend some support to this 

 view. The frequent occurrence of diabetes in those predisposed by 

 inheritance to neurotic conditions, or in those whose daily habits entail 

 much nerve strain, and the aggravation of the symptoms which is likely 

 to follow when a diabetic patient experiences some nervous shock, all 

 point in this direction. 



Diabetes is common in locomotive engineers and in the captains of 

 ocean liners that is, in men who in the performance of their daily duties 

 are frequently put under a severe nerve strain. It is apparently in- 

 creasing in men engaged in occupations that demand mental concentra- 

 tion and strain, such as in professional and business work. Cannon 23 

 found glycosuria in four out of nine students after a severe examination, 

 but only in one of them after an easier examination.* In the urine of 

 twenty-four members of a famous football squad, sugar was found pres- 

 ent in twelve immediately after a keenly contested game. Anxiety and 

 excitement were responsible for its appearance, for five of the twelve 

 were substitutes who did not get into the game. 



Although these nervous conditions, by excitement of hepatic glyco- 

 genolysis, produce at first nothing more than an excessive discharge of 

 sugar into the blood a condition which is exactly duplicated in our 

 laboratory experiments by stimulation of the nerve supply of the liver 

 their repetition may gradually lead to the development of a permanent 

 form of hyperglycemia. To prevent the repetition of these transient 

 hyperglycemias must be one of our aims in the treatment of early stages 

 of the disease. 



Although there can be no doubt that the glycogenic function of the 

 liver is subject to nerve control, it is probable that its control by hor- 

 mones is of equal if not greater importance. This dual control of a 

 glandular mechanism is by no means unique for the glycogenic function, 

 for we have already seen it to exist in the case of the gastric glands 

 and the pancreas, and it is probable that it also exists in the case of 

 the thyroid. It may well be that the nerve control of the glycogenic 

 function has to do only with those transitory changes in sugar produc- 

 tion that would be demanded by sudden activities of muscle, and that 

 the hormone control has to do with the more permanent process of build- 

 ing up and breaking down of glycogen to meet the general metabolic 

 requirements of the tissues. 



*We have been unable to confirm this observation even though the examinations were made 

 unusually "nerve-racking." 



