48 THE INVOL UNTAR Y NER VO US S YSTEM 



The substance is absolutely ineffective on all tissues which are 

 innervated by the nerve cells of the cranial or sacral outflows. 

 In adrenalin then we possess an extraordinary means of check- 

 ing the conclusions arrived at by stimulation of the nerves be- 

 longing to the thoracico-lumbar outflow. The selective action 

 of adrenalin is not on the central nervous system, for it acts more 

 powerfully on the denervated organ and even after all the nerves 

 going to the organ have been allowed to degenerate. 



This intimate relationship between the action of adrenalin and 

 that of the sympathetic nervous system is most extraordinary and 

 the reason for it will be considered later. It has naturally been 

 utilized for the investigation of such doubtful cases as the exist- 

 ence of motor nerves to the blood vessels in the case of the arteries 

 of the brain, of the lungs, and of the heart, in all of which the 

 existence of vaso-constrictor nerves has been doubted. In all 

 these cases the action of adrenalin has proved the existence of 

 such nerves, even though their action is weak. Thus Biedl and 

 Reiner have seen contraction of the blood vessels of the brain 

 upon direct application of adrenalin, and Protopopow and 

 Wiggers found there was a distinct diminution in the outflow- 

 ing blood upon the addition of adrenalin to the fluid circulating 

 through the brain. With respect to the lung vessels Brodie and 

 Dixon could find no evidence of constriction by adrenalin, but 

 Plumier and Wiggers found a distinct diminution in the rate of 

 flow through the lungs when fluid containing adrenalin was sent 

 through. Flintier and Starling also obtained a distinct rise of 

 pressure in the pulmonary artery, by adding adrenalin to the per- 

 fused blood in the heart lung preparation. Tribe also found 

 that if the pressure in the pulmonary artery was not above the 

 normal, adrenalin always caused a marked diminution of flow 

 through the lung ; and also obtained some evidence of vaso-con- 

 striction by direct stimulation of the stellate ganglion. In the 

 case of the coronary vessels of the heart adrenalin is said to cause 

 dilatation not constriction, but Brodie and Cullis think this is due 

 to the strength of adrenalin used being too great. When they sent 

 an artificial circulation through the rabbit's heart, to which a weak 

 dose of adrenalin had been added, the first effect, which lasted 

 as long as 80 seconds, was a diminution of flow through the 

 coronary vessels followed by a marked increase of flow. This 

 dilatation, which has often been observed, can be explained 



