436 THE NERVOUS REGULATION OF THE BLOOD-VESSELS 



renalis, which in turn communicates with the mesenteric gangUon. 

 By measuring the blood-supply of this organ with the aid of the 

 stromuhr, Burton-Opitz^ has shown that the stimulation of this plexus, 

 or of single nerves thereof, leads to a constriction of its blood-vessels 

 and therefore to a diminution in its vascularity. This plexus also 

 contains dilator fibers. The same results may be obtained by the 

 excitation of the greater splanchnic nerve of the same side or, as Brad- 

 ford^ has shown, by the stimulation of the fibers emerging from the 

 tenth to the thirteenth spinal nerves (dog). This investigator also 

 states that the kidney receives dilator fibers which are derived from 

 the eleventh, twelfth and thirteenth thoracic spinal nerves. 



By cutting the renal plexus the kidney is converted into a passive 

 organ. The renal blood-vessels relax and permit a greater quantity 

 of blood to enter this organ; moreover, this augmentation becomes the 

 more pronounced, the greater the arterial blood pressure. Thus, the 

 vascularity of a denervated kidney can be increased very readily by 

 the stimulation of either splanchnic nerve, because, as we have seen, 

 the ensuing constriction of the portal blood-vessels raises the systemic 

 blood pressure and, hence, also the arterial influx into this now non- 

 resistant organ. • The stimulation of the central end of the divided 

 renal plexus usually gives rise to a reflex increase in the general blood 

 pressure (pressor action), whereas weak and infrequent stimuli gen- 

 erally produce a reflex vasodilatation (depressor action). It should 

 also be remembered that the innervation of the kidneys is unilateral.^ 



That the splanchnic nerves are capable of exerting a true vasomotor 

 influence upon the adrenal bodies has not been thoroughly established.^ 

 Certain evidence, however, has been presented by Elliott^ and Von 

 Anrep^ to show that they govern the secretory activity of these glands. 

 Thus it was found that the stimulation of the aforesaid nerves gives 

 rise to an immediate outpouring of adrenin into the venae suprarenales, 

 whence this product reaches the general arterial circulation by way of 

 the inferior cava. Here it incites its characteristic reaction consisting 

 in a general vasoconstriction. The time which elapses between the 

 moment of the stimulation of the splanchnic nerve and the beginning 

 of this vasomotor reaction, amounts to about 12 to 15 seconds, in a dog 

 weighing about 15 kg. 



This outpouring of adrenal substance is a constant physiological 

 process, tending to preserve the vasomotor tonus and to cause tem- 

 porary increases in blood pressure. Keeping this fact clearly in mind, 

 we are now in a position to consider more fully the influence which the 

 stimulation of the splanchnic nerve exerts upon the general blood 



1 Pfliiger's Archiv, cxxiii, 1908, 553. 



2 Jour, of Physiol., x, 1889, 358. 



3 Burton-Opitz, Am. Jour, of Physiol., xl, 1916, 437. 



-* Biedl, Pfliiger's Archiv, Ixvii, 1897, 433; also: Burton-Opitz and Edwards, 

 Am. Jour, of Physiol., xliii, 1917, 408. 

 s Jour, of Physiol., xliv, 1912, 374. 

 « tbid., xlv, 1912, 307. 



