The regulation of the supply of oxygen to the tissues 139 



obtained by section of the cervical sympathetic ; for this constrictor 

 nerve is cut throughout the experiment, and was actually being- 

 stimulated at the very time that the dilatation was observed. Clearly 

 the dilatation takes place in spite of this stimulation ; the cause of 

 the dilatation, whatever it may be, is something which overrides the 

 excitation of the vaso-constrictor fibres. 



Perhaps the most natural assumption to make is that there are 

 dilatator fibres mixed with the constrictor fibres in the sympathetic. 

 This assumption was made by Carlson and his colleagues, Greer, Becht 

 and McLean ((5) , who, independently of us, observed the vaso-motor 

 phenomena which we have described. The second of the two papers 

 on the subject which appeared from his laboratory, in its closing 

 words states the issue as between true dilatator fibres, such as are 



80 100 120 140 



160 180 



FIG. 75. Ordinate = Rate of blood-flow through the submaxillary gland. | = Stimulation 

 of cervical sympathetic commences and lasts throughout. The figures represent 

 graduation of a tube along which the blood from the gland flowed. -0021 c.c. =1 

 graduation of tube. Abscissa time in seconds. 



assumed in the chorda tympani and local metabolic products. "If 

 there are some vaso-dilatator fibres... we should be able to show their 

 presence by cutting out the vaso-constrictors by chrysotoxine and 

 stimulating the vaso-dilatator apparatus by adrenalin, as chrysotoxine 

 seems to affect the vaso-constrictors, not the vaso-dilatators." 



The same issue had been pointed out to me at a meeting of the 

 Physiological Society by Dale ; in effect it is this : Ergotoxine (or 

 chrysotoxine) does not paralyse the chorda tympani dilatator fibres, 

 but does paralyse the sympathetic constrictor fibres ; if therefore 

 there are fibres in the sympathetic which are functionally chorda 

 tympani fibres, then after the administration of ergotoxine and 

 paralysis of the constrictor fibres, stimulation of the sympathetic 

 will produce the same effect on a small scale as stimulation of the 



