40 PROTEOLYTIC PANCREATIC FERMENT 



tal to the symptom-complex ; he does not accept the physio- 

 logical importance of secretin for normal production of the 

 pancreatic secretion, and, while willingly acknowledging the 

 existence of a nervous mechanism as operative in the 

 process, does not recognize a humoral factor. However, it 

 must be insisted upon that, from the studies of Bayliss and 

 Starling, the substance in intestinal extracts which depresses 

 the blood pressure is not identical with secretin, and that 

 secretin-containing solutions can be prepared which are 

 apparently free from the former. It must be acknowledged 

 that a clear insight into the matter has by no means been 

 attained. 



The attendant difficulties may be the more readily appre- 

 hended if it is recalled that the nervous mechanism qon- 

 cerned in the pancreatic secretory process is a complex one 

 and is really very little understood. We know that the pan- 

 creas receives its nervous impulses both from the vagus and 

 the splanchnic ; both nerves furnish fibres to the blood ves- 

 sels of the gland, and from stimulation of either according to 

 circumstances there may be induced either increase or in- 

 hibition of the secretion. C. Schwarz 12 was able to show 

 that cholin can influence the pancreatic secretion in one way 

 or the other according to the quantity injected, on the one 

 hand inhibiting the flow through its excitation of the vagus 

 centre, on the other inducing activity by stimulation of 

 peripheral autonomous secretory nerves. It may therefore 

 be appreciated without further discussion that it is difficult 

 if not impossible to come to a satisfactory conclusion as to 

 the identity or differentiation of any of the active con- 

 stituents of organic extracts from simple comparison of 

 their influences upon the pancreatic secretion and from other 

 physiological factors. Until we are able to deal with chem- 

 ically definite substances, it is to be feared we will be unable 

 to escape from such contradictions. 



C. Schwarz (Vienna), Centralbl. f. Physiol., 23, 337, 1909. 



