712 METABOLISM 



animal after ligation of the portal vein. To the clinical worker the value 

 of these results lies in the fact that they furnish experimental proof that 

 a so-called latent case of diabetes that is, one that has a low tolerance 

 value for carbohydrates may be prevented from developing into a 

 severe case by proper control of the diet. Attempts to show whether or 

 not there are any conditions which might bring about improvements 

 in animals that were just diabetic have not as yet been sufficiently made 

 to warrant any conclusions that could help us in the treatment of human 

 cases. It has been suggested that stimulation of the internal pancreatic 

 secretion might occur when the secretion into the intestine is kept as 

 low as possible by selecting a diet that does not require the pancreatic 

 enzymes for its digestion and that the increased internal secretion might 

 be of value in delaying the onset of diabetes in susceptible cases. 



The Pathogenesis of Pancreatic Diabetes 



The certainty with which diabetes results from pancreatectomy in dogs, 

 as well as the frequent occurrence of demonstrable lesions of the pan- 

 creas in diabetes in man, leaves no doubt that this gland must be in some 

 way essential in the physiological breakdown of carbohydrates in the 

 normal animal, but how, we can not at present tell. All we know is 

 that the first change to occur after the gland is removed is a sweeping 

 out of all but a trace of the glycogen of the liver, although the muscles may 

 retain theirs; indeed, in the cardiac muscle there may be more than 

 the usual amount." 8 Nor can any glycogen be stored in the liver when 

 excess of carbohydrates is fed. After the glycogen has disappeared, 

 gluconeogenesis sets in, so that the tissues come to melt away into sugar, 

 and all the symptoms of acute starvation, associated with certain others 

 that are possibly due to a toxic action of the excess of sugar or other 

 abnormal products in the blood, make their appearance. 



So far it might be permissible to consider an overproduction of glu- 

 cose as the sole cause of the hyperglycemia of pancreatic diabetes, just as 

 we have seen it to be the cause of these forms of hyperglycemia that re- 

 sult from stimulation of the nervous system; but this can not be the case, 

 for another very definite abnormality in metabolism becomes evident 

 namely, an inability of the tissues to burn sugar. This fact is ascer- 

 tained by observing the respiratory quotient. When glucose is added 

 to the blood in the case of a completely diabetic animal, no change oc- 

 curs in the quotient. 



There are, therefore, two essential disturbances of carbohydrate 

 metabolism in pancreatic diabetes overproduction of sugar and aboli- 

 tion of the ability of the tissues to use it. It becomes important for UP 

 to see whether the tissues exhibit this inability to use sugar when they 



