HEALTH AM) DISEASE 



is more bean-shaped, is situated rather farther backwards than the right, 

 touching the spleen in front, and weighs about 25 ozs. The external .sur- 

 face of each kidney is smooth, and on its inferior surface is in great part 

 covered by the peritoneum or lining membrane of the belly. The inner 

 border is deeply notched to form the hilus of the kidney, wherein is lodged 

 the pelvis — a small sac or receptacle into which the urine is first received. 

 Here also the renal arteries enter, the renal veins emerge, and the ureter 

 begins and continues its course from the pelvis to the bladder. Each 

 kidney is enclosed in a dense membrane or capsule, which in health can be 

 easily stripped off the proper substance 

 of the organ, whilst in some forms of 

 disease it is firmly adherent. If a kid- 

 ney be divided by a horizontal cut (fig. 

 132), into an upper and a lower half, 

 a difference in colour will be noticed 

 between the outer cortical portion and 

 the inner medullary portion. The outer 

 or cortical portion is of dark reddish- 

 brown colour and finely granular aspect; 

 the inner or medullary portion is lighter 

 in colour and presents a number of fine 

 lines, converging towards the cavity in 

 the centre of the kidney named the 

 pelvis. Both the cortical and medullary 

 zones are chiefly composed of delicate 

 tubes — the urinary tubules, — together 

 with many blood-vessels, and the differ- 

 ence in their aspect is due to the difference in the form and arrangement 

 of these tubuli uriniferi. 



If we follow one of these tubuli (fig. 133) from its commencement in 

 the outer or cortical substance of the organ to the point where it terminates 

 by opening into the pelvis of the kidney, we find that it begins with a little 

 dilatation or bulb termed the capsule of Malpighi (fig. 133, c), about y-55-th 

 of an inch in diameter, from which proceeds a cylindrical and much- 

 contorted tube that lies in the cortical zone and has a diameter of about 

 -g-jjoth of an inch. The tube then enters the internal or medullary zone, 

 where, becoming much narrowed, it forms a long loop, the loop of Henle, 

 and having reascended towards the outer or cortical zone becomes once 

 more coiled, and finally joins with others to form a collecting tube. These 

 winding tubes are lined by a layer of cells which secrete or separate the 

 urine from the blood, after which the collecting tubes convey it into the 



Fig. 132.— Section through Kidney 

 Ureter. B, Renal capsule, c, Cortex. 



.Medulla. E, 1-ienal vessels. F, Pelvis. 



