THE ABDOMEN 825 



the kidney is a ball of convoluted capillary bloodvessels, which is 

 enclosed within a capsule of Bowman, whereas a Malpighian 

 corpuscle of the spleen is a collection of lymphoid or adenoid 

 tissue which is a localized expansion of the external or lymphoid 

 coat of the small arteries in the interior of that organ. 



Veins — Veins of the Cortex. — These are called the interlobular 

 veins. Some of them commence on the surface of the kidney 

 beneath the capsule, from which they return blood, and these are 

 called vencB stellatce, because the venous radicles which give rise to 

 them converge to a point, and so present a star-like appearance. 

 Others originate in the plexuses around the uriniferous tubules. 

 The interlobular veins terminate by joining the convexities of the 

 venous arches, which are situated between the cortex and the 

 Malpighian pyramids. 



Veins of the Medulla. — ^The veins of the Malpighian pyramids 

 commence in plexuses which surroimd the excretory tubes or ducts 

 of Bellini in the apical parts of the papillary zones, and they are 

 called vencB rectcB. As these traverse the pyramids they are collected 

 into bundles of straight vessels, which open into the concavities of 

 the cortico-medullary venous arches, 



Cortico-medullary Venoits Arches. — ^These arches, w^hich are com- 

 plete, are situated between the cortex and the Malpighian pyramids, 

 where they lie alongside of the incomplete arterial arches. They 

 derive their blood from the interlobular veins of the cortex, and 

 the vense rectae of the Malpighian pyramids. The veins which 

 proceed from these arches pass between the pyramids to the sinus 

 of the kidney, where they unite to form the renal vein, which termi- 

 nates in the inferior vena cava. 



Lymphatics. — ^These consist of two groups, superficial and deep. 

 The superficial lymphatics, which are few in number, form a plexus 

 in the fibrous capsule, and communicate with lymph spaces 

 between the uriniferous tubules in the outer part of the cortex. 

 They terminate by joining the deep lymphatics at the hilum. 

 The deep lymphatics accompany the bloodvessels, and communicate 

 with lymph spaces between the uriniferous tubules of the cortex 

 and boimdary layer. On emerging at the hilum they receive the 

 superficial lymphatics, and then pass to the lateral group of lumbar 

 glands. 



Nerves. — ^The kidney receives numerous nerves from the renal 

 plexus, which derives its fibres from (i) the aortico-renal ganglion, 

 in which the small splanchnic nerve terminates ; (2) the coeliac 

 plexus ; and (3) the aortic plexus. If there is a least splanchnic 

 nerve present it reinforces the renal plexus. The nerve-fibres are 

 partly sympathetic, partly spinal through the small and least 

 splanchnic nerves, and in part derived from the right pneumo-gastric 

 through the coeliac plexus. They accompany the arterial branches, 

 and ramify upon the walls of the vessels and uriniferous tubules. 



Excretory Apparatus of the Kidney.— This consists of the calices 

 or infundibula, pelvis, and ureter. 



