THE CARBOHYDRATES AND THEIR METABOLISM 261 



which indicates a low carbohydrate combustion which can only be ex- 

 plained on the basis of low glycogen reservoir. This is in conformity with 

 the findings of Cramer and Kraus (li)13j who found that after thyroid 

 ingest ion the liver does not retain glycogen as well as before. 



The effect of the thyroid on carbohydrate metabolism, therefore, is 

 purely through its interference with glycogen formation and mobilization. 

 Its effect is similar to that of adrenalin and sympathetic stimulation, and 

 the probabilities are, that they all act through the same channel. 



Influence of the Pituitary Gland. The pituitary gland, similar to 

 the thyroid, has a tendency to affect the carbohydrate metabolism when 

 in a state of hyperactivity. Gushing (1913) found that the administra- 

 tion of extract of the posterior lobe of pituitary was followed by a reduc- 

 tion in the carbohydrate tolerance and by a mobilization of glycogen. On 

 the other hand, patients with acromegaly, who are supposed to suffer from 

 an hy pel-functioning of the anterior lobe of the pituitary, very frequently 

 show evidences of lowered carbohydrate tolerance and of glucosuria. 



Borchhardt (1908) found glucosuria in 40 per cent of his cases of 

 acromegaly, but in no case of tumor of the pituitary that was not aero- 

 mega lie. 



There is at present no reason to believe that the pituitary extracts 

 affect the carbohydrate metabolism in any other way than do the extracts 

 of the adrenals and thyroid. All three seem to have the power of stimulat- 

 ing the sympathetic nervous system, and the reaction they produce differs 

 only in degree. The effect of adrenalin is most powerful; those of the 

 thyroid and pituitary will only bo determined after their respective ef- 

 fects have been studied with their active principles. 



Just as the pat ell a r reflex may be used clinically for roughly de- 

 termining the state of nervous tension of an individual, so the carbo- 

 hydrate tolerance test may be used clinically for determining roughly 

 the state of an individual's tonus of the sympathetic nervous system. But 

 we cannot employ that at present to differentiate between affections of the 

 thyroid, pituitary or adrenal. 



The Intermediary Metabolism of Carbohydrates 



All the processes of metabolism aim at two objects, first to build up 

 and maintain the body structure, second to produce the material that can 

 be used for dynamogenetic purposes. It is most surprising that in spite 

 of the large number of chemical compounds that play a role in metabolism, 

 only very few are "fit to burn." In the chapter on protein metabolism it 

 was brought out that fully fifty-eight per cent of the protein molecule 

 passes through a glucose stage. Over ten per cent of the fat molecule 

 (the glycerol fraction) passes through a glucose stage, and all of the 



