530 STRUCTURE OF THE KIDNEYS. 



Malpighiana, or, according to Krause and the recent investigations of Mr. 

 Toynbee,* by anastomoses and cascal extremities. The average d'ameter 

 of the tubuli uriniferi in the cortical portion of the kidney is the -^^ of an 

 inch, of which about two-thirds are occupied by a nucleated epithelium, 

 the remaining third representing the area of the tube. According to Mr, 

 Bowman, the epithelium is ciliated in that part of the tubule which is neai 

 the Malpighian body, and which, according to the same authority, is very 

 much constricted. 



In the cortical portion of the kidney are contained a multitude of minute, 

 red, globular bodies, the corpora Malpighiana, or glomeruli. Each Mal- 

 pighian body, about T J$ of an inch in diameter, is composed of a plexus 

 of capillary vessels, and, in addition, according to Mr. Toynbee, of a coil 

 of an uriniferous tubule ; the tuft of capillaries and the coil of the tubule 

 both being enclosed in a thin, membranous capsule. According to Mr. 

 Bowman, the capsule of the Malpighian body is the origin of the uriniferous 

 tubule expanded into a globular form for the reception of the capillary 

 tuft. The capillary vessels of the vascular tuft are arranged in loops 

 closely packed together, and surrounded by an epithelium which is conti- 

 nuous with a similar structure lining the inner surface of the capsule. 

 They 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 com- 

 municate with the efferent vessels of other Malpighian bodies and consti- 

 tute a venous plexus. 



The cones or mamillary processes of the interior of the kidney are in- 

 vested by mucous membrane, which is continuous at their apices with the 

 uriniferous tubuli, and is reflected from their sides so as to form around 

 each a cup-like pouch, or calyx. The calices communicate with a com- 

 mon cavity of larger size, situated at each extremity, and in the middle 

 of the organ ; and these three cavities, the infundibula, constitute 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 ana- 

 tomy of the foetus in the succeeding Chapter. 



The Ureter, (ou^ov, urine, rr^eiv, to keep,) the excretory duct of the kid- 

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

 nearly eighteen inches in length ; it is continuous superiorly with the pel- 

 vis 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 blad- 

 der, 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 against 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, and the calices are composed of two 

 coats, an external or fibrous coat, the tunica propria ; and an internal 

 mucous coat, which is continuous with the mucous membrane of the 



On the intimate Structure of the Human Kulney, &c. Medico-Chirnrgicnl Trans- 

 actions, vol. xx ix., 1846. 



