THE FUNCTIONS OF THE DIGESTIVE ORGANS. 527 



conditions, it was found that even water is to be regarded as a direct 

 stimulant of the pancreas. The extractive substances from beef, on the 

 other hand, did not cause any stimulation. Quite recently the influence 

 of alcohol upon the pancreatic secretion has been studied, 1 and in this 

 case it was found that, while the amount of the secretion was augmented, 

 the juice then had less digestive power. Alcohol also appears to have a 

 direct action upon the ferments or their antecedents. If alcohol is added 

 to pancreatic juice, then the digestive action of the latter upon starch and 

 albumin is much lessened, while on the other hand the action upon the 

 fat-splitting ferment is favorable. 



It was highly important to establish the fact that the psychic factor 

 also played a considerable part in the work of the pancreas. The vagus 

 provides this organ as well as the stomach with secretory nerves. Further- 

 more, it is also claimed that the splanchnic sends fibres to the pancreas. 

 It was extremely difficult to determine whether the secretion of the pan- 

 creatic gland was effected by a fictitious meal, and for the following 

 reasons: We have seen that the secretion produced by the membrane 

 of the stomach, and its glands, is greatly dependent upon psychic influ- 

 ences. A subsequent increase in the amount of pancreatic juice secreted 

 may, therefore, take place on account of the increased acid production in 

 the stomach; i.e., in this case the pancreas would be merely indirectly 

 affected by the fictitious meal. Now we know that the secretion of the 

 stomach does not take place at once, but only after a latent period of about 

 four and one-half minutes. The pancreatic secretion similarly begins two 

 or three minutes after it has become stimulated by acid. It was found 

 that the augmented pancreatic secretion resulted within two or three 

 minutes after the beginning of the fictitious meal, so that from this the 

 conclusion may be drawn that the gland is directly influenced psychically. 

 It is important that the pancreatic gland, in spite of its dependence upon 

 the other organs, especially the stomach, still has a considerable amount 

 of independence, so that even in the absence of stimulation from the 

 stomach, it can perform its functions. Experience gained from day to day 

 teaches us that if, for example, there is an insufficient amount of hydro- 

 chloric acid formed in the stomach, digestion is not prevented, but still 

 progresses to a quite remarkable extent. 



We must in addition consider a very important discovery for which we 

 will have to thank two Englishmen, Bayliss and Starling. 2 They showed 

 that by means of 4 per cent hydrochloric acid a substance could be extracted 

 from the mucous membrane of the intestine which, when introduced into 

 the circulation, increased the flow of pancreatic juice. They called this 

 substance secretin. They have assumed that this substance is not present 



> A. Gizelt: Zentr. Physiol. 19, 769 (1906). 



2 J. Physiol. 30, 61 (1903); Proc. Roy. Soc. 73, 310 (1904). 



