FORMATION OF URINE 



571 



I. Structure of the Kidney. 



{This must he studied practically.) 

 Each kidney presents a depression or hilus on its inner aspect 

 from which the ureter, the duct of the kidney passes, and by 

 which the renal artery enters and the renal vein emerges. The 

 nerves and lymphatics of the organ pass along with these. The 

 whole organ is enclosed in a fibrous capsule, from which processes 

 of fibrous tissue carrying small blood-vessels enter the organ. 



Fk;. 226. —Diagram of the Structure of the Kidney. i/.P., Malpighian 

 pyramid of the medulla ; M.R., medullary ray extending into cortex ; 

 L., labyrinth of cortex; M.B., a Malpighian body consisting of the 

 glomerular tufi and Bowman's capsule; P.C.T., a proximal convoluted 

 tubule ; H.L., Henle's loop on the tubule ; D.C.T., distal convoluted 

 tubule ; C.T., collecting tubule ; R.A., branch of renal artery, giving 

 off I. LA, interlobular artery, to supply the glomeruli and the con- 

 voluted tubule; ZL.i?., interlobular artery bringing blood back from 

 the cortex. 



The ureter opens from the basin of the kidney, and into this 

 the renal tissue projects as pyramidal processes. 



This renal tissue is clearly divided into a thin outer cortex 

 and an internal medulla. This latter is again subdivided into 

 a paler pyramidal part, and a redder part between this and the 

 cortex — the boundary zone. The medulla extends out into the 

 cortex in a series of long medullary rays (fig. 226), so that the 



