196 INFLUENCE OF NERVOUS SYSTEM ON PANCREAS. [BOOK II. 



all secretion has ceased. The fluid secreted in the early periods 

 of digestion is very viscous, and soon gelatinizes on standing; it is 

 highly coagulable. It contains from 6 to 10 per cent, of solid 

 matters. As digestion progresses the juice becomes less viscid, its 

 coagulability diminishes and its solid matters also become less. So 

 that even in the physiological condition we may have a compara- 

 tively non-viscid and sparingly coagulable juice.' 



But, in most cases, when a pancreatic fistula has been established 

 matters do not continue as above, and the departure from normality 

 is evidenced, firstly, by the secretion becoming continuous, secondly, 

 by its becoming abundant and non-viscous, as well as by another 

 most important character. The normal juice possesses the power, 

 firstly, of digesting proteids, secondly, of converting starch into 

 dextrins and maltose, thirdly, of emulsionizing and decomposing 

 the neutral fats. Now the non-viscous, abundant, secretion obtained 

 from the majority of cases of permanent fistulae only possesses the 

 second and third of these properties ; it is, that is to say, destitute of, 

 at least very poor in, the proteolytic ferment. 



Influence of Though the close dependence of the secretion of 



the nervous pancreatic juice upon the various stages of the diges- 

 system upon tive process must clearly depend upon nervous control, 

 the pancreatic our knowledge of the nervous mechanism is not as 

 complete as might be wished. The following are the 

 principal facts yet ascertained: 



1. When the nerves going to the pancreas are all divided, secre- 

 tion of a diffluent juice is set up and continues ; this is analogous to 

 the paralytic saliva which flows after division of all the nerves 

 supplying the submaxillary gland. 



2. Electrical stimulation of the medulla oblongata sets up 

 secretion if in abeyance, and increases it if already in process. 



3. A useful method, and the only one really at the disposal 

 of the experimenter, for setting up pancreatic secretion in animals 

 with pancreatic fistulae is to inject a little ether into the stomach 2 : 

 this agent sets up a flow of pancreatic juice which is characteristic 

 of the condition of the gland at the time : thus, if the ether be 

 injected five or six hours after food, there is obtained a flow of viscid 

 and concentrated juice ; on the other hand, if it be injected fifteen 

 hours after a meal, it is always diffluent. 



4. Secretion is arrested when the act of vomiting is provoked ; 

 also by stimulation of the central end of the vagus, and of sensory 

 nerves generally, the arrest in this case lasting long after the 

 stimulation has ceased. The cessation is probably due to a contrac- 

 tion of the blood-vessels of the pancreas. 



1 The author is indebted for the summary of all the facts which are here stated to 

 Heidenhain's account in Hermann's Handbuch, to which the reader is referred, see 

 Vol. v. p. 194 et seq. 



2 Kiihne, Lehrbuch der physiol. Chem. p. 113. 



