THE SUPRARENAL SYSTEM 301 



However this may be, the vascular distribution in the suprarenal 

 that is to say, the arrangement of the arteries leading to it and 

 the manner in which they communicate with the great central 

 vein leading from it is very remarkable. Flint's excellent work 

 and the experiments of Srdinko have supplied very exact infor- 

 mation concerning the suprarenal in mammals, and this is supple- 

 mented by Landau's corrosion preparations. Based upon the 

 representations of these authors, the suprarenal circulation appears 

 to be as follows. 



A large number of the arteries which enter the suprarenal 

 break up in the cortex into a network of capillaries, which traverse 

 the connective tissue septa in a manner which accords with the 

 structure of the latter, being straight in the zona fasciculata, and 

 forming a network in the zona reticularis. After traversing the entire 

 cortex, the blood reaches the medulla in wide sinus-like vessels; 

 in the medullary capillaries it flows round the chromaffine cells, 

 and afterwards collects in small veins which increase in size, and 

 all of which open into the great central vein. The arteries, and 

 probably the afferent veins which supply the suprarenal capsule 

 and the portions of the zona glomulerosa abutting on to it, also 

 break up into capillaries, \vhich again combine to form the vens& 

 revehentes. 



A certain number of the arterial vessels, the arterias per- 

 forantes (Srdinko) penetrate the cortex and reach the medulla 

 directly ; there they break up into capillaries, which also follow 

 the course of the cell columns, and finally discharge their blood 

 into the great efferent vein. This separate blood supply of the 

 medulla is the outcome of the secondary invasion, during foetal 

 life, of the interrenal organ by adrenal tissue. 



This peculiar vascular distribution has been interpreted in 

 the following manner (Poll). It is suggested that, in the first 

 place, the blood from the body which has become deprived of its 

 adrenalin contents, is carried by the vessels which exclusively 

 serve the medulla directly to the adrenalin-forming cells, that these 

 part with the secretion with which they are charged, and that the 

 blood, with its reinforced adrenalin contents, is again returned to 

 the general circulation. In the second place, the venous blood dis- 

 charged from the cortex contains the products of the metabolism of 

 this tissue, which constitute the raw material for the elaboration of 

 adrenalin, and this raw material is immediately conveyed to the 

 medulla. It would seem from this that, in certain species in which 

 the adrenalin demand is very high, as in mammals and birds, 

 there is a combination on the part of the two apparatuses which 

 contribute to the elaboration of adrenalin, thus establishing a 

 perfected method of production. In species in which the two 

 suprarenal systems are independent, the semi-product supplied by 

 the interrenal bodies is carried through the entire circulation 

 before it reaches the site of its ultimate completion, namely, the 

 adrenal tissue. 



