SECTS. 184, 185.] 



THE KIDNEYS. 



403 



OF THE URINARY ORGANS. 



§ 184. The urinary organs consist of the two kidneys, — two 

 true glands of a tubular structure, which prepare the urine,— and 

 of the excretory passages, the ureters, the urinary bladder, and the 

 urethra. 



§ 185. The kidneys are composed of a secreting parenchyma, 

 surrounded by certain envelopes. In the latter, two coats are 

 enumerated j the one scarcely deserves the name of a special coat, 

 for it only consists of loose connective tissue, with numerous fat-cells 

 in its meshes : it has received the name of the capsula adiposa, or 

 fat capsule. The true fibrous envelope, tunica propria s.albuginea, 

 is a whitish investment, thin but firm, formed of ordinary connective 

 tissue, and numerous fine net-works of elastic fibres. It closely 

 envelops the kidney, and, at the hilus, becomes applied to the 

 calyces and the vessels, without being continued into the interior 

 of the organ, although, even at 

 the hilus, it closely surrounds the 

 parenchyma as far as the cortical 

 substance extends. 



The secreting parenchyma (fig. 

 166) is sharply limited by the 

 fibrous capsule, and consists, when 

 viewed with the naked eye, of 

 two parts — the medullary and the 

 cortical substance. The former of 

 these appears in the form of from 

 eight to fifteen isolated conical 

 masses, with their apices towards 

 the hilus — the Malpighian pyra- 

 mids (fig. 166 e) — whilst the lat- 

 ter (fig. 166 h) forms the entire 

 cortex of the organ, and sends 

 inwards, between the separate 

 pyramids, partitions which extend 

 up to the hilus — the Column® 

 Bertini (fig. 166/7). The cortical 

 substance appears to be connected through the whole kidney with- 

 out any interruption. Microscopically examined, however, the 



D D 2 



A section through the middle of the kidney 

 of a child, a. ureter; 6. pelvis; c. calyces; 

 d. papilla ; e. Malpighian pyramids ; /. Fer- 

 rein'i pyramid of Authors ; g. septa Bertini; 

 k. outer part of the cortical substance. 



