1014 THE URIXARY ORGAXS 



covered above by the peritoneum of the lesser sac, ^Yhich sei)arates it from the 

 stomach; and below, near its internal inferior angle, it is crossed by the ui)i)er 

 border of the pancreas and the splenic artery. Externally it is in contact Avith 

 the upper extremity of the spleen, which passes a little beliind it, and its inner 

 border is separated from its aorta by the fibres of the diaphragm. 



Accessory suprarenal bodies are often present in the neighbourhood of the 

 principal organs. 



Structure. — On section the organ is found to V)e covered by a thin fil;trous 

 capsule ^hich sends trabecular processes between the cellular elements of its proper 

 substance. The parenchyma consists of a peripheral portion or cortex, of 

 yellowish colour, excei^t in its deepest layer, which is darkly pigmented, and a 

 central portion or medulla, soft and greyish, and tending to break 'doAvn under 

 decomposition in such a manner as to give the appearance of an irregular cavity 

 (whence the name suprarenal ' capsule'). 



Vessels and nerves. — It is richly supplied both with vessels and nerves. Its 

 arteries are derived from three sources — the aorta, the phrenic, and the renal — 

 and pierce the organ in various places, but chiefly on the anterior surface along a 

 furrow sometimes called the hilum. The veins terminate on the right side in the 

 vena cava, and sometimes by means of small l)ranches in the phrenic and renal 

 trunks; on the left, in the left renal vein. The lymphatics pass to the renal 

 glands, which, like the suprarenal bodies, themselves contain a good deal of pig- 

 ment. The nerves form a rich and complex interlacement, and are derived chiefly 

 from the solar and renal plexuses, but include filaments from the splanchnics. and 

 according to some authors from the phrenic and vagus also. It is disproportion- 

 ately large in early foetal life, and has nearly reached its full growth at the time of 

 birtii. 



THE REXAL DUCTS 



The excretory duct of the kidney (figs. 607, 611, 616) is a musculo-mucous 

 canal, expanded and in-egularly Ijranched a1)ove, narrow and of fairly uniform 

 dimensions in the rest of its course. At its origin in the sinus renalis it a]4)ears 

 in the form of a number of short tubes, usually eight or nine, called calices, (^ach 

 of which embraces the papillary extremity of a pyramid of Malpighi two or three 

 lines above its apex, or occasionally two papillae may be connected with a single 

 calyx. The calices average about a third to half an inch (8 to 12 mm.) in length, 

 and open directly or by means of intermediate tuljes (infundibula) into two short 

 passages, the superior and inferior pelves, which in turn coml)ine after a longer 

 or shorter course to form the common pelvis. The inferior and larger pelvis has 

 a diameter of about two-fiftlis of an inch (10 mm.); the superior is about one-third 

 less. Occasionally a third or middle pelvis is present. 



The common pelvis varies greatly in different subjects. It usually appears as 

 a more or less funnel-shaped portion of the canal, Avider above (about three-fifths 

 of an inch — 15 mm. ),' where it lies between the two lips of the hilum; narrow below, 

 Avhere it arches downwards and inwards to become continuous with the relatively 

 uniform portion of the duct known as the ureter proper. In some cases, how- 

 ever, it can scarcely be said to exist as a dilatation. I'nder ordinary circumstances 

 it is flattened from before backwards, its anterior and posterior Avails being in con- 

 tact, and its chaimel represented by a fissure. It is in relation behind Avith the 

 posterior lip of the hilum, from Avhich it is separated 1)v more or less adipose tissue 

 continuous with tlie fatty capsule, and occasionally Ity an irregular branch of the 

 renal artery. The renal vein and artery lie in front, iml)edded in fat, and anterior 

 to these structures is situated the descending portion of the duodenum on the right 

 side, and the pancreas on the left. 



The ureter extends from the termination of the pelvis to the l)ladder, running 

 in a kind of lymph-space betAveen the lamina of the subperitoneal tissue. It is a 

 tube of about a fifth of an inch (5 mm.) in diameter Avhen distended, and is fairly 

 uniform in size, except about two inches beloAv tlie kidney, Avhere a slight constric- 

 tion is usually foimd (Bruce Clark). Its length is variously stated, but the average 

 in the male adult may he taken as aliout tAvelve inches (30 cm.), the right being 

 usuallv a little the shcjrter. The excessive estimates sometimes given de^icnd upon 



