142 TOPOGRAPHICAL ANATOMY OF THE 



is in contact with the second tiexure of the duodenum and the dorsal 

 sac of the caecum. The caudal end of the left kidney — broader and 

 blunter than the cranial extremity — is related to various coils of the 

 intestinal mass. 



The medial border (margo medialis) of both glands is indented by 

 the hilus. This border of the right kidney is related to the caudal vena 

 cava, the right adrenal gland and the right ureter. The left kidney 

 is medially related to the abdominal aorta, the left adrenal and the 

 left uretei*. 



The lateral border (margo lateralis) of both kidneys is divisible into 

 two parts, meeting at an angle that, because of the triangular con- 

 formation of the organ as a whole, is much more distinct and acute in 

 the right gland. The lateral border of the right kidney is followed by 

 the duodenum ; while the corresponding border of the left gland is in 

 contact with the spleen and the small colon. 



The renal hilus^ (hilus renalis) is a sharp indentation on the medial 

 border of the kidney and affords entrance and exit for blood vessels, 

 nerves, lymphatics and the ureter. Of the three main structures 

 connected therewith the renal artery is the most ventral, the renal vein 

 most dorsal, and the ureter intermediate in position. It should be 

 noted that, though branches of the renal artery enter at the hilus, others 

 pierce the capsule of the gland at various points on the ventral surface. 



If the lips bounding the hilus be separated, a cavity of some extent 

 and depth, the renal sinus'' (sinus renalis), will be disclosed. The 

 most important object contained within the sinus is the funnel-like 

 commencement of the ureter. 



Interior of tJie kidney. — The surface of the kidney is covered by a 

 strong fibrous capsule that can readily be stripped ofl' except where it is 

 continuous with the sheaths of the various structures entering the 

 orsan at or in the neighbourhood of the hilus. 



A horizontal section of the kidney should be made by entering the 

 knife at the lateral border and carrying it to the hilus. When this has 

 been done, the cut surface will reveal the presence of two distinct 

 portions of kidney tissue. The cortical substance, which is towards the 

 exterior, is reddish-brown in colour and granular in texture ; whereas 

 the medullary substance is pale and striated. In the dark boundary 

 zone between the two substances the cut ends of numerous large 

 vessels should be noted. These indicate the former limits of the 

 primitive lobes, readily recognisable in the fcKtal organ, of which the 

 kidney is composed. 



1 Hilum (whence nihilum and nihil, nothing) [L.], a small part, a trifle. 

 - Sinus [L.], a bay, hollow, cavity. 



