THE CIRCULATION THROUGH SPECIAL ORGANS 437 



pressure as well as upon the blood flow through the kidneys. We 

 have just seen that the excitation of this nerve leads not only to a 

 constiiction of the blood-vessels in the corresponding kidney, but also 

 to a liberation of an extra amount of adrenin from the neighboring 

 suprarenal body. As soon as this agent has reached the arterial system, 

 a general vasoconstriction is incited which also includes the blood- 

 vessels of the two kidneys. But, as the renal blood-vessels on the 

 side of the stimulation have already been constricted in a direct way, 

 the adrenin only serves the purpose of augmenting the primary effect 

 in this particular organ. On the opposite side, on the other hand, it 

 incites its characteristic effect. Thus, it will be seen that the stimula- 

 tion of the splanchnic nerve eventually leads to a constriction of the 

 vessels of both kidneys, but the one occuring on the side of the excita- 

 tion appears almost immediately after the make of the current and is 

 due primarily to a direct motor influence, whereas the one in the 

 opposite organ takes place later on and is the result of the ingress of 

 adrenin. 



In the second place, we are now in a position to offer a detailed 

 explanation of the character of the rise in the general blood pressure 

 invariably following the stimulation of the splanchnic nerve. It has 

 been observed by Johansson^ that this increase does not present a single 

 summit, but two, the initial one being somewhat smaller than the 

 second. ElHott and Von Anrep have succeeded in showing that the 

 second elevation is dependent upon the outpouring of adrenin, because 

 the ligation of the suprarenal veins or the removal of the suprarenal 

 bodies as a whole causes this summit to disappear completely. To 

 summarize: Under ordinary experimental conditions the stimulation 

 of the splanchnic nerve produces a vasoconstriction in the organs in- 

 nervated by it. The transfer of blood associated therewith reUeves 

 the splanchnic organs of a certain quantity of blood and forces it 

 into the general circulation. This change gives rise to the primary 

 rise in the arterial blood pressure. Secondly, it also leads to the libera- 

 tion of adrenin which, on being flushed into the arterial system, causes 

 a general vasoconstriction which is associated with an augmentation 

 of the constriction already produced in the splanchnic organs. In 

 consequence of this extensive secondary involvement of the blood- 

 vessels, the general blood pressure is again raised. The second summit 

 of the splanchnic rise in blood pressure is therefore directly attributable 

 to the discharge of adrenin. 



The Vasomotors of the Intestines. — With the exception of the 

 upper segment of the duodenum the intestine is innervated by fibers 

 arising in the mesenteric gangUon of the solar plexus. These fibers 

 pass along the mesenteric arteries. The stromuhr experiments of 

 Burton-Opitz^ have shown that the division of this postganglionic 

 path is followed by an engorgement of the intestinal blood-vessels, 



1 Archiv fiir Anat. und Physiol., 1891, 103. 



2 Pfluger's Archiv, cxxiv, 1908, 469. 



