THE CARBOHYDRATES AND THEIR METABOLISM 259 



that by far the greatest portion can be removed with impunity. Of course 

 there is a certain degree of variation in different animals, but in the great 

 majority as much as four-fifths of the organ may be removed without pro- 

 ducing any diabetes. When only very small portions of the pancreas are 

 left intact, the animals develop a tendency towards alimentary glucosuria, 

 but no true diabetes. The transition from this stage to that of true dia- 

 betes is entirely dependent upon the amount of pancreatic tissue left intact. 



The most convincing proof that the absence of the pancreas was re- 

 sponsible for the glucosuria was presented by Minkowski in experiments 

 in which he showed that animals that had their pancreas entirely removed 

 did not develop diabetes if a portion of the pancreas was transplanted sub- 

 cutaneously. 



Since this was established attempts have been repeatedly made to ex- 

 tract a hormone from the pancreas and supply that to the depancreatized 

 animals with the hope that the pancreatic function would be replaced. 

 All attempts have failed, and the reason for it may be found in the fact 

 that the digestive ferments of the pancreas destroy that hormone. 



Two very interesting series of experiments were performed by Forsch- 

 bach (1908 and 1913) and by A. J. Carlson and F. M. Drennan (1911). 



Forschbach performed an operation on two dogs in such a way that 

 the blood of dog A was made to circulate in dog B. He then completely 

 removed the pancreas of dog B. As long as dog B received the blood 

 from dog A, dog B did not develop any glucosuria, proving conclusively 

 .that the blood of dog A carries a substance (hormone) which takes the 

 place of the pancreatic function. This was later corroborated by Hedon 

 (1909), who found that the glucosuria of depancreatized dogs disap- 

 peared soon after he transfused it with the blood of a normal dog. 



Carlson's experiments were based upon principles similar to the above, 

 namely, that the blood carries a substance that is supplied to it by the 

 pancreas. He therefore performed complete pancreatectomy in animals 

 that were in the latter stages of pregnancy. Either very slight or no glu- 

 cosuria set in. After the birth of the puppies, however, the mother be- 

 came diabetic, proving that the fetus was able to supply the mother with 

 its pancreatic hormone ; true diabetes setting in after the fetal supply was 

 removed. 



There is therefore no more question to-day but that the pancreas is 

 directly concerned with carbohydrate metabolism. It enables the body 

 to oxidize glucose and it enables the body to convert glucose into glyco- 

 gen. In its absence, or in case of its failure to functionate properly, the 

 two functions disappear and the body loses the power to oxidize glucose 

 and it also loses the power to convert glucose into glycogen, both of which 

 result in hyperglucemia and glucosuria. 



We are now confronted by the problem of how the pancreas exerts its 

 influence on the carbohydrate metabolism. It will be a conservative esti- 



