igS INTERNAL SECRETION 



pathetic innervation. Substances such as barium, which exercise 

 a direct influence upon the unstriated musculature of the vessels, 

 produce an increase in blood-pressure even under these condi- 

 tions. Dixon concludes from this that adrenalin acts on the 

 sympathetic nerve endings. 



That the effect of adrenalin upon the blood-vessels is identical 

 with that produced by stimulation of the sympathetic nerves could 

 not be doubted if proof were forthcoming that, where the sym- 

 pathetic innervation is inhibitory and therefore vaso-dilator, the 

 effect of adrenalin is also to produce vaso-dilation. 



Dastre and Morat point out that the sympathetic system fur- 

 nishes vaso-dilator fibres to the bucco-facial region, and R. Brad- 

 ford discovered that it also supplies vaso-dilators to the kidneys. 

 Elliott was unable to obtain a primary vaso-dilation by means of 

 adrenalin in any part of the body; upon the principle that the 

 vaso-dilator nerves react to very slight stimuli, he reduced his 

 doses to the minimum, but was still unsuccessful. Sollmann and 

 Pari observed an occasional dilation of the renal vessels after 

 adrenalin, while Jonescu has recently pointed out that minimal 

 doses are followed by a constriction of the renal vessels. 



Elliott and Dale were successful in proving the vaso-dilator 

 properties of adrenalin by means of chrysotoxin. After the intra- 

 venous injection of 100 mg. of chrysotoxin, stimulation of the 

 splanchnic nerve is followed, not by a rise, but by a fall in 

 blood-pressure. Under similar conditions adrenalin also produces 

 a fall in pressure, which lasts for about the same length of time 

 as the rise which takes place under normal conditions. This fall 

 in blood-pressure, whether brought about by the agency of 

 adrenalin or by electric stimulus, is probably due to stimulation of 

 the vaso-dilator nerve endings. 



The vaso-dilator effect of adrenalin may also be seen in the 

 coronary vessels of the heart. It has long been known that 

 adrenalin rather increases than diminishes the circulation of blood 

 through the heart, and this result has been attributed to the in- 

 creased cardiac activity. Elliott showed that adrenalin will 

 produce an increased circulation in a portion of ventricle flooded 

 with Locke's fluid. 



Owing to the fact that portions of arteries respond actively 

 to the influence of adrenalin after their removal from the living 

 body, a great deal of information has been obtained concerning 

 the effect which adrenalin has upon the vessels and its dependence 

 for this effect upon the nature of their innervation. The experi- 

 ments of Bayliss, MacWilliam and v. Frey show that isolated 

 blood-vessels, if suitably treated, will remain alive and sensitive to 

 stimulus for days. Prompted by the results of these experiments, 

 O. B. Meyer succeeded in working out a method by which the 

 influence of different drugs upon the vessels might be studied. A 

 circular strip is cut from an artery and suspended lengthwise in 



