491 THE URINARY APPARATUS. 



5. The Supra-renal Capsules. (Fig. 247.) 



Situation Form. The supra-renal capsules (or adrenal*} are two small 

 bodies applied to the lower face of the kidneys, in front of the hilus, and 

 close to their inner border. 



They are elongated from before to behind, flattened on both sides, and 

 irregularly lobulated on their surface. Their length is from 2 to 2^ inches, 

 and width from If to 1 inches. They have not the same volume, the 

 right being larger than the left. 



Relations. A large amount of connective tissue, vessels, and nervous 

 filaments attach these bodies to the neighbouring organs. The right is 

 related, in front, to the liver ; above, to the right kidney ; and inwardly, to 

 the posterior vena cava and the ramifications of the solar plexus. The left 

 does not touch the liver or spleen, but, by its inner border, is applied against 

 the posterior aorta and great mesenteric artery. 



STRUCTURE. At present, anatomists are not agreed as to the structure of 

 the supra-renal capsules. The following is what is probably most reliable 

 in this difficult point in normal histology. 



These organs offer an enveloping membrane and parenchyma. 



The enveloping membrane is fibrous, and sends off, from its inner face, 

 prolongations which pass into the parenchyma and form cylindrical spaces, 

 subdivided by transverse lamellae. These spaces are named glandular 

 cavities ; but the septa soon become thin, and disappear almost completely, 

 leaving nothing but some very few trabeculse of connective tissue. 



The parenchyma is divisible into two layers: the cortical and medullary 

 substance. The first is of a dark-brown colour ; the second is yellow and 

 soft, and does not show any cavity in its centre ; that which has been 

 described is the result of the destruction of its proper elements, which soon 

 change after death. 



The glandular cavities of the cortical substance are filled with nucleated, 

 granular, and often fat cells in the adult animal ; near the central substance 

 these cavities only contain a single cell. 



The medullary substance has, for its basis, a very delicate reticulum, 

 supporting cells analogous to those of the cortical substance, and stellate 

 elements which Luschka considered were nerve cells. 



Vessels and nerves. Like the kidneys, which are contiguous to them, the 

 supra-renal capsules receive a large quantity of blood, compared with their 

 small volume. The arteries are branches of the neighbouring vessels : the 

 mesenteric and renal. They form a very delicate plexus in the parenchyma. 

 (They keep to the stroma of the trabeculee; consequently, their finest 

 ramifications are found in the secondary septa of the cortical substance, 

 where they form elongated plexuses, which are rounder in the medullary 

 portion. In the middle of the latter, the venous ramuscules unite, and give 

 rise to a considerable trunk, the vena supra renalis, on which the organ is 

 placed as on a pedicle. It is this vein which constitutes the debated 

 cavity.) 



The veins are satellites of the arteries in the tissue of the organ, and pass 

 into the renal vein or posterior vena cava. The lymphatics are scarce. 



The supra-renal bodies receive many ganglionic nerves derived from the 

 solar plexus, and whose mode of termination is unknown. (As mentioned 

 by Chauveau, the nerves of these organs nre extremely numerous, they being 

 more abundantly supplied than any other structure of the kind in the body ; 

 a large number of small branches enter the cortical portion, to become 



