748 FRED C. KOCH 



juice, when similarly injected, does cause a secretion, whereas if intro- 

 duced into the intestines it requires the addition of an acid in order to 

 act as stimulant to pancreatic secretion. Aqueous extracts of duodenal 

 mucous membrane, when injected intravenously, were found very efficient 

 by Popielski, whereas the simple introduction of water into the intestine 

 did not cause a pancreatic secretion. He also found ordinary fats con- 

 taining small amounts of free fatty acids to stimulate when placed in the 

 duodenum. He interprets his findings as proof of a stimulation of nerve 

 endings in the duodenum, and thus reflexly a stimulation of the pancreas. 

 The evidence on the whole is, however, favorable to the humoral path of 

 stimulation. But there is no evidence proving the actual formation of 

 secretin in the duodenal contents. If it is formed it is due to acid acting 

 on the mucous membrane of the duodenum and causing the formation of 

 secretin in the intestinal wall. 



Many of the earlier observers reported that atropin does not inhibit 

 pancreatic secretion when it is brought about by secretin or by dilute 

 acid acting in the duodenum, whereas the secretion brought about by 

 cholin can easily be inhibited by atropin. Popielski (1907) and Uhl- 

 mann (1918) have, however, shown that when the doses are properly 

 adjusted one can inhibit the secretion in either case. This is very likely 

 correct, in view of similar observations by Luckhardt, Keeton and Koch 

 (1920) on the effect of atropin on gastric secretion as brought about by a 

 meal, by gastrin, or by histamin. It is very likely entirely a question of 

 the relative doses of secretin and atropin employed. Such is at least the 

 case as to gastric secretion. The fact that atropin may inhibit the action 

 of secretin does not necessarily invalidate the humoral theory, for atropin 

 acts on cells directly as well as on the nervous system. 



Relation of Secretin to the Internal Secretion of the Pancreas. Very 

 soon after the discovery of secretin action many attempts were made to 

 establish a relationship between the duodenum and the internal secretion 

 of the pancreas. A number of studies were conducted in which it was 

 attempted to show a decreased prosecretin content in duodenal mucous 

 membrane in cases of diabetes mellitus and in depancreatized dogs. It is 

 obvious that the two conditions are by no means identical. Bainbridge 

 and Beddard (1906) found very little or no prosecretin in five out of six 

 cases of diabetes mellitus. Later, however, Bainbridge (1908) found 

 prosecretin present without doubt in eight out of nine cases of human 

 diabetics; only one case of diabetic- coma, a seventeen-year-old boy, 

 yielded an extremely weak secretin solution. The authors also were not 

 able to influence the prosecretin content of the duodenum in dogs by acid 

 poisoning, nor by extirpation of the pancreas. Evans (1913) found a loss 

 of 33 to 95 per cent in the secretin concentration obtained from the duo- 

 denal mucous membrane after removal of the pancreas. The higher 

 loss occurred six days after the operation. In one dog 1/6 of the pancreas 



