590 STRUCTURE OF THE KIDNEYS. 



substance of the organ will be found to be studded with a multitude of 

 minute, red, globular bodies ; these are the Malpighian bodies or 

 glomeruli. Each Malpighian body is about the -j-i-j. of an inch in 

 diameter, and is composed of a tuft of capillary vessels enclosed 

 within the extremity of an uriniferous tube, so that the number of 

 Malpighian bodies corresponds with the number of tubuli uriniferi. 

 The presence of the capillary tuft necessarily produces a dilatation of 

 the uriniferous tube ; beyond the tuft the tube presents a constriction, 

 and then assumes its proper diameter, namely, ^-g-g- of an inch. Two- 

 thirds of the diameter of the tube are occupied by a nucleated 

 epithelium, which in the constricted portion just mentioned is pro- 

 vided with cilia, and in the dilated part or capsule which receives the 

 capillary tuft is gradually lost. The capillary vessels of this vascular 

 tuft are arranged in loops, closely packed together, without any bond 

 of connecting tissue, and are derived from a small artery, which, after 

 piercing the capsule, immediately divides in a radiated manner into 

 several branches. From the interior of this little vascular ball a vein 

 proceeds, smaller than the corresponding artery, and pierces the 

 capsule close by the artery, to communicate with the efferent vessels of 

 other Malpighian bodies and constitute a venous plexus.* 



The Cones or pyramids are composed of minute straight tubuli 

 uriniferi of about the diameter of a fine hair ; they divide into parallel 

 branches in their course, and terminate by minute openings upon the 

 apex or papilla of each cone. The papillae are invested by mucous 

 membrane, which is continuous with the tubuli, and forms a cup-like 

 pouch, the calyx, around each papilla. The calices communicate with 

 a common cavity of larger size, situated at each extremity, and in the 

 middle of the organ ; and these three cavities, the infundibula, consti- 

 tute by their union the large membranous sac, which occupies the 

 hilus renalis, the pelvis of the kidney. 



The kidney in the embryo and foetus consists of lobules. See the 

 anatomy of the foetus in the succeeding Chapter. 



The Ureter (ow^av, urine, rfyttv, to keep), the excretory duct of the 

 kidney, is a membranous tube of about the diameter of a goose-quill, 

 and nearly eighteen inches in length ; it is continuous superiorly with 

 the pelvis of the kidney, and is constricted inferiorly, where it lies in 

 an oblique direction between the muscular and mucous coats of the 

 base of the bladder, and opens upon its mucous surface. Lying along 

 the posterior wall of the abdomen, it is situated behind the peritoneum, 

 and is crossed by the spermatic vessels ; in its course downwards it 

 rests upon the anterior surface of the psoas, and crosses the common 

 iliac artery and vein, and then the external iliac vessels. Within the 

 pelvis it crosses the umbilical artery and the vas deferens in the male, 

 and the upper part of the vagina in the female. There are sometimes 

 two ureters to one kidney. The ureter, the pelvis, the infundibula, 



* For this account I am indebted to the excellent paper of Mr, Bowman, 

 " On the Structure and Use of the Malpighian Bodies of the Kidney," &c. 

 published in the Philosophical Transactions for 1842. 



