898 PHYSIOLOGY OF DIGESTION AND SECRETION. 



of the normal process is itself incompletely known, the defect 

 caused by the failure of the pancreatic hormone becomes cor- 

 respondingly difficult to define. Clark* reports some recent ex- 

 periments in which he perfused the heart and pancreas, singly and 

 together, with a Ringer solution containing dextrose, the per- 

 fusion being carried out under aseptic conditions. When the 

 pancreas alone was perfused the dextrose suffered a change in 

 optical rotation without any alteration in reducing power. 

 When the heart and pancreas were perfused together or in sequence 

 the dextrose suffered a diminution in both optical rotation and re- 

 ducing power. Since both of these properties were restored in 

 part toward normal on subsequent hydrolysis of the perfused 

 liquid it would seem that the dextrose had undergone a con- 

 densation to some form of polysaccharid. The author suggests 

 that the pancreas furnishes some substance, presumably an enzyme, 

 which causes a preliminary change in the dextrose of an unknown 

 nature, but probably a condensation. When this material is 

 brought to the heart or other tissues there is a further change to a 

 form of carbohydrate which is especially adapted for utilization. 

 This action of the pancreas seems to be limited to dextrose; 

 levulose, at least, is not affected in a similar way. Other investi- 

 gators adopt an entirely different view of the relation of the pancreas 

 to carbohydrate metabolism. They believe that the internal secre- 

 tion of the pancreas regulates in some way the output of sugar 

 from the liver. In the absence of this secretion the liver gives off its 

 glycogen as sugar too rapidly, the sugar contents of the blood are 

 thereby increased (hyperglycemia) above normal, and the excess 

 passes out in the urine. The large amount of work that has been 

 done upon pancreatic diabetes, as well as diabetes mellitus in man, 

 seems to favor the general view that in these conditions the dif- 

 ficulty lies not in the processes of glycogenesis or glycogenolysis, 

 but in the consumption of sugar by the tissues. In pancreatic 

 diabetes certainly the balance of evidence supports the theory of 

 an internal secretion on the part of the pancreas, which plays an 

 essential r61e in the normal process of sugar consumption in the 

 tissues. One very striking bit of evidence in this direction is 

 furnished by Carlson f and his co-workers. They find that if 

 extirpation of the pancreas is effected in a pregnant dog near term, 

 the animal does not exhibit glycosuria until the pups are born or 

 are removed by cesarean section. The internal secretion from the 

 fetal pancreas suffices to protect the mother. 



* Clark, "Journal of Exp. Medicine," 1917. 



t Carlson and Drennan, "American Journal of Physiology," 28, 391, 1911; 

 also 36, 217, 280, 1915, and "Journal of Biological Chemistry," 13, 465, and 

 17, 19. 



