332 THE ADRENAL, GENERAL MOTOR, AND VAGAL SYSTEMS. 



the organ is thought to transform. We shall, therefore, begin 

 with this channel, which brings to the liver essentially venous 

 blood, since it contains that utilized by four organs the 

 stomach and the intestines, the pancreas and the spleen in 

 which the metabolic products include, besides those incident 

 upon ordinary tissue-waste, food metabolites, physiological 

 toxics, etc. 



As is well known, there exist in the liver's secretions dis- 

 tinct evidences of association with splenic haematopoietic or 

 hasmolytic functions. The liver is known to modify the com- 

 position of the blood as it passes through it, but the purposes 

 of the alterations involved are not established. 



The path from the spleen to the portal vein, through the 

 splenic vein, is a direct one, and the blood the spleen sends 

 to the liver is not, therefore, submitted to modifications in 

 transit by any other organ, though the splenic vein receives a 

 few branches from the pancreas and stomach. Still, these are 

 mere tributaries to a common channel, and, as the' arterial 

 supply comes directly from the cceliac plexus, we can say that 

 the spleen receives nothing but pure, freshly-oxygenated blood 

 in great quantities. Indeed, the splenic artery is remarkably 

 large for the dimensions of the organ, and we can easily account 

 for the so-called "ague-cake" and the temporary enlargement that 

 occurs during malarial and other fevers when we include supra- 

 renal overactivity in the pathogenesis of these phenomena. 



To this we cannot ascribe, however, the post-prandial 

 splenic enlargement, which attains its maximum about five 

 hours after an ordinary meal, since we now know how inde- 

 pendently of suprarenal overactivity and merely through nerv- 

 ous influence an organ's function can be excited and governed; 

 indeed, sympathetic and pneumogastric again unite here to 

 account for a passive period and for an active period: that 

 of gradual enlargement. "The turgescence of the spleen 

 seems to be due to a relaxation both of the arteries and of 

 the muscular tissue of the capsule and of the trabecula?" says 

 Professor Foster: evidence that we are again dealing with 

 vasoconstriction of some arterioles to shift the blood-stream 

 into the functional areas, a repetition of what we have found 

 to exist in other organs. Obviously the constriction and shift- 



