The regulation of the supply of oxygen to the tissues 147 



Effect of stimulation of chorda tympani on the 

 atropinised submaxillary gland. 



same degree as it would be in the normal gland. The second assurance 

 that must be given is that this increased metabolism is not a fictitious 

 one caused by the increased rapidity of the flow. This was a matter 

 which greatly exercised me as it proved very difficult to devise satis- 

 factory control experiments ; however after testing numerous methods 

 of producing vaso-dilatation artificially, Prof. Franz Miiller (7) drew 

 my attention to the possibilities of yohimbin for this purpose, and in 

 collaboration we tested the matter and found that even the very 

 great amount of dilatation which can be induced by injecting small 

 quantities of this drug directly into the submaxillary artery does not 

 cause increased oxygen to be used by the gland. 



(2) Bayliss (8) and Asher' 9 ' pointed out another direction in which 

 it might be possible to find the necessary evidence for the proof of 

 the " title " of the vaso-dilatator fibre. They showed that when the 

 central end of the depressor nerve is stimulated on the one side, say 

 the right, the vessels of the left submaxillary gland dilate, whether 

 or no the sympathetic is cut, provided that the chorda tympani is 

 intact. The deduction is that a reflex stimulation of the chorda 

 tympani takes place which produces vaso-dilatation, and here it should 

 be said that there is no flow of saliva ; on the other hand it must also 

 be said that the phenomenon is only obtainable in a fraction of the 

 experiments. 



Here again an appeal may be made directly to measurements of 

 the oxygen used by the gland to give an answer as to whether or no 



102 



