182 



ANATOMY FOB, NUKSES. [CHAP. XVI. 



The structure of the kidney. The kidney is a secreting gland, 

 constructed upon the general plan of a compound secreting 

 gland, but possessing special features peculiar to itself. If we 

 cut a kidney in two lengthwise, it is seen that the upper end of 

 the ureter expands into a basin-like cavity, into which the solid 

 portion of the kidney projects in conical-shaped masses. This 

 dilated cavity of the ureter is called the pelvis or basin of the 

 kidney, and this pelvis is irregularly subdivided into smaller, 



cup-like cavities, called calices, 

 which receive the pointed pro- 

 jections of the kidney substance. 

 The substance of the kidney 

 is readily seen by the naked eye 

 to consist of two distinct parts : 

 an outer, darker, and more 

 solid portion, called the cortex 

 (bark), and an inner, lighter 

 striated portion, called the me- 

 dulla (marrow), which is not a 

 solid mass, but more or less 

 distinctly divided into pyra- 

 midal - shaped sections. The 

 pointed projections or papillw 

 FIG. 106. -SECTION THROUGH THE Q f the pyramids are received 

 KIDNEY, SHOWING THE MEDULLARY AND L J 



CORTICAL PORTIONS, AND THE BEGIN- by the irregularly disposed CUp- 



NING OF THE URETER. (Henie.) Ct, like cavities of the pelvis. The 



cortex ; M, medulla ; Py, papilla of pyra- 

 midal section, projecting into one of the bulk of the kidney Substance, 



artery- U ureter. *' ^^ **' ^ b th ln the COI>teX and medulla ' 



is composed of little tubes or 



tubules, closely packed together, having only just so much 

 connective tissue as is sufficient to carry a large supply of 

 blood-vessels and a certain number of lymphatics and nerves. 

 The different appearance of cortex and medulla is due to shape 

 and arrangement of tubules and blood-vessels. 



Examined under the microscope, it is seen that the urinifer- 

 ous tubules begin as little rounded dilatations, called capsules, 

 in the cortex of the kidney. These capsules are joined to the 

 tubules by a constricted neck, and the tubules, after running a 

 very irregular course, open into straight collecting tubes, which 

 pour their contents through openings in the pointed ends or 



