THE KIDNEYS : 559 
Examination with a pocket lens shows that the cortex is imperfectly divided 
into lobules (Lobuli corticales). Each lobule consists of an axial radiate part (Pars 
radiata), surrounded by a convoluted part (Pars convoluta). The former appear 
as ray-like prolongations from the bases of the pyramids (hence also termed medul- 
lary rays), and consist largely of narrow, straight or slightly flexuous tubules (limbs 
of the loops of Henle). The convoluted part is granular in appearance, and con- 
sists largely of the renal corpuscles and convoluted tubules. 
The renal pelvis (Pelvis renalis) is the dilated origin of the excretory duct. 
It lies in the sinus of the kidney, and it is funnel-shaped, but flattened dorso-ven- 
trally. The renal crest! (Crista renalis) projects into the outer part of the pelvis 
in the form of a horizontal ridge with a concave free edge. The tubules of the 
middle part of the medullary substance open on this crest into the pelvis. The 
tubules from each end of the kidney do not open into the pelvis proper (Recessus 
medius), but into two long, narrow diverticula (Recessus terminales), which pro- 
ceed from it toward the poles of the kidney. The wall of the pelvis consists of 
three layers. The external fibrous coat or adventitia is continuous with the sup- 
porting tissue of the kidney. The muscular coat consists of longitudinal and 
Fie. 500—Castr or Rieut Renat Petvis (a), Re- Fie. 501.—Cast or Lerr Renat Petvis (a), RECESSES 
CESSES (c, c’), AND ORIGIN OF URETER (b) oF HoRSE. (c, ce’), AND OrtctIn oF URETER (6) oF HORSE. 
(After Dumont.) (After Dumont.) 
circular fibers. The mucous coat does not cover the renal crest nor is it continued 
into the diverticula of the pelvis. It has a yellowish tinge, and forms numerous 
folds. It contains compound tubular glands (Glandule pelvis renalis), which 
secrete the thick, viscid mucus always found in the pelvis.” 
Renal Tubules.—The parenchyma or proper substance of the kidney is composed of the 
small renal or uriniferous tubules (Tubuli renales), which are very close together and have a 
complicated course. Each tubule begins in a thin-walled, spherical dilatation or capsule (Cap- 
sula glomeruli), which is invaginated to receive a tuft of looped capillaries termed a glomerulus; 
these two structures constitute a renal corpuscle; the corpuscles are visible as minute red or 
dark spots in the convoluted part of the cortex. Succeeding this is a short narrow neck, beyond 
which the tubule becomes wide and convoluted, forming the proximal convoluted tubule, and 
enters the radiate portion of the cortex. It then gradually narrows and enters the intermediate 
zone; becoming very narrow and nearly straight, it descends for a variable distance into the medul- 
lary substance, turns sharply upon itself, and returns to the cortex, forming thus the loop of Henle, 
with its descending and ascending limbs. In the convoluted part of the cortex it widens and 
becomes tortuous, constituting the distal convoluted tubule. The tubule then narrows, enters a 
medullary ray, and opens with other tubules into a straight collecting tubule; this passes axially 
through a pyramid, and unites with other collecting tubules to form the relatively large papillary 
ducts, which open into the renal pelvis. 
Stroma.—The interstitial tissue forms a reticulum throughout which supports the tubules 
_ _ ! The crest is the result of fusion of the papillz or apices of the pyramids in the embryo and 
is therefore also known as the papilla communis. 
F * There are goblet cells in the epithelium of the pelvis which doubtless concur in the secretion 
of mucus. 
