148 Chapter IX 



there is increased chemical action taking place in the gland. My 

 experience has been that in those cases in which I have been able 

 to obtain the reflex there has been increased oxidation, whilst in 

 the cases in which I have obtained no increased blood flow the 

 oxidation has remained normal. But the experiments which I per- 

 formed were few. 



The answer then to the question, " Is it possible to demonstrate 

 that the vaso- dilatation which follows upon stimulation of the 

 chorda tympani involves a definite neuro-muscular vaso-dilatator 

 mechanism?" is "It is not possible on the evidence at hand either 

 to prove it or disprove it." The functional dilatation involved may 

 be held to account for all known cases of dilatation in the sub- 

 maxillary, but it is not proved to do so. The dilatation which takes 

 place on stimulation of the atropinised gland is of relatively short 

 duration. It is not impossible that under normal circumstances 

 dilatation may be instituted by dilator fibres and maintained by 

 metabolic products. 



The pancreas. The transition from the submaxillary gland to 

 the pancreas is a natural one. Adrenalin does not cause any flow 

 of juice however from the pancreas; we must therefore give the 

 appropriate stimulus, namely secretin. The effect of secretin on the 

 vessels of the pancreas formed the subject of a research by Otto 

 May (10) , who showed by plethysmographic tracings that there was an 

 increase in the volume of the pancreas when it was secreting and 

 also that there was an increase in the " pulse volume " on the tracing. 

 May attributes the dilatation to metabolic products acting on the 

 vessels, and it is certain that there is ample evidence of increased 

 chemical activity taking place in the pancreas itself inasmuch as 

 the amount of oxygen which the pancreas uses is increased about 

 four-fold when secretin is eliciting a flow of juice. The proof in the 

 case of the pancreas is however less satisfactory than in the case of 

 adrenalin in the submaxillary gland, because solutions of secretin 

 usually, and in the case of May's experiments admittedly, contained 

 depressor substance. The "depressor" substance is depressor in 

 virtue of the fact that it dilates the vessels all over the body. 



Therefore the question really is this : Does the solution con- 

 taining secretin and depressor substance produce a greater degree 

 of dilatation in the pancreas than the same solution would do if the 

 secretin were absent ? The answer to this question is given by May 

 in the following words: "...there was an expansion of the small 



