300 INTERNAL SECRETION 



Jourdain found that it was present in more than thirty species, 

 and he discovered that fluid injected into the vena externa passed 

 readily into the vena interna, and vice versa. He believes, how- 

 ever, that the communication between the two vessels is not direct 

 but that it is effected by means of a network of capillaries, the 

 vena externa representing the afferent, and the vena interna the 

 efferent, portion of the portal system of the suprarenal. He was 

 unable, however, to bring direct proof in support of his theory. 



Since Jourdain, there has been, as far as my knowledge goes, 

 no further investigation into the relationship between the two 

 suprarenal veins in birds. It seemed to me advisable that the 

 matter should be elucidated, and Professor F. Hochstetter was 

 kind enough to lend me his help in the matter. Up to the present 

 it has not been found possible to obtain the venous capillary 

 network of hens by means of corrosion preparations. But I was 

 able to follow the course of the vessels very exactly in a series 

 of sections obtained from the embryo of a sparrow immediately 

 before hatching. I found that the vein which approaches the 

 suprarenal from the lateral side, enters the organ, forms large 

 sinuous spaces within it, and probably afterwards breaks up into 

 capillary vessels. In sections taken more towards the cranium, 

 large veins filled with blood are seen at the median surface of the 

 suprarenal; these are the ven^e suprarenales ; they run in an 

 oblique direction towards the vena cava and open into it. The 

 arterial vessels also approach the organ upon the median side. 



It is evident from this that a suprarenal portal system is 

 present, not only in reptiles, but in birds, and that blood is con- 

 veyed to the suprarenals by veins as well as by arteries. 



In mammals, however, blood is supplied to the suprarenals 

 by way of the arteries only. According to Pettit, conditions 

 resembling the portal system of birds are encountered in certain 

 mammalian species. The last intercostal vein proceeds directly 

 to the suprarenal, and opens into the vena cava at the place where 

 the kidneys form an angle with it, in which angle the suprarenal 

 lies, close against the walls of both vessels. If one or more 

 branches from the suprarenal veins empty themselves into the 

 intercostal vein, the appearance produced will suggest that the 

 latter is not an efferent, but an afferent, vein. Pettit draws atten- 

 tion to a peculiar venous distribution which he has observed in 

 monkeys and in certain rodents (kangaroo, sheep), and which has 

 been observed in man by some French anatomists (Ouenu and 

 Lejars). Single branches proceed from the venous arches of the 

 adipose capsule of the kidney to the suprarenal, which they cover, 

 finally penetrating into the interior of the organ. Pettit is 

 inclined to regard these venous branches as indications of a 

 suprarenal portal system. 



It is, however, very doubtful whether these rudimentary venas 

 afferentes suprarenales have a functional significance in mammals. 



