THE KIDNEYS. 241 



vessels, and by the peritoneum, which passes over their in- 

 ferior surface, or over the fat which may cover them. Tiie 

 kidneys lay upon the top of the peritoneum, and conse- 

 quently are without the abdominal sac ; they are conglome- 

 rate glands ; and when cut into present two distinct portions. 

 The cortical or outer part is of a dull dark red, of a granular 

 structure, which dips into the other substance ; the cortical 

 mass may be regarded as the convolutions of the emulgent 

 capillaries, around the minute terminations of the urinary 

 ducts. The second substance, called the medullary part, is 

 lighter in colour than the last, and presents a vast number 

 of radiating tubes, which collect into minute cones or 

 papillfE. These papillee are clothed by a mucous membrane, 

 which is cup-shaped, and continuous with the lining mem- 

 brane of the tubes ; each is called a calyx. The calices point 

 into canals, or grooves, continuous with the pelvis of the 

 kidney, and named the infundibula. The pelvis, into which 

 the infundibula lead, is nothing more than an enlargement 

 at the beginning of the ureters, situated without the kidney. 

 The urine then is secreted from the capillaries of the emul- 

 gent arteries, coiled round the minute ends of the renal 

 ducts ; whence it passes into the tubuli uriniferi, or tubular 

 portion of the kidneys, to flow towards the calices ; from 

 which it falls into the infundibula. By the infundibula it is 

 passed to the pelvis, thus into the ureters, and so into the 

 bladder. The arteries of the kidneys are so large as to be 

 supposed to carry one-eighth of the whole blood of the body 

 (see Plate IV. E) to these comparatively small organs. 

 The large trunks of the arteries emerge from the aorta, 

 immediately behind the anterior mesenteric artery {Fig 

 13 ./) ; the left is much shorter than the right, from the 

 inclination of the aorta to that side (Plate YV . A) ; each 

 trunk penetrating its kidney by two or three divisions (Fig 

 13 ./). The emulgent veins {Plate IV. F) arise from the 

 capillaries of the artery, and follow the direction of that 

 vessel. The nerves of the kidney are furnished from the renal 

 plexus, formed by the par vagum and sympathetic nerves ; 

 its lymphatics are to be seen accompanying the veins. 



The ureter {Plate IV. C) passes out at the posterior 

 part of its appropriate kidney, is continued backwards, 

 inclining towards the bladder ; when, becoming connected 



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