i6a 



PHYSIOLOGY FOR BEGINNERS 



ff*. 



vein. With scissors cut into the hilus, or, if you can, cut 

 open the end of the ureter along its length and trace it 

 into the kidney. The ureter dilates in the kidney into a 

 funnel-shaped cavity called the pelvis of the kidney. 

 The inner wall of the cavity is whitish, except for masses 

 of the reddish substance of the kidney projecting into it. 

 These projections into the pelvis are called the pyramids 

 of the kidney. If you look carefully you will see that they 

 are finely pitted on the surface. These pits are the openings 

 of the minute tubules of which the substance of the kidney 

 is composed. Cut the kidney in two halves, on the flat, 

 cutting from the hilus towards the convex border. The outer 



part of the kidney is of a differ- 

 ent colour from the rest, being a 

 darkish-brown, while the central 

 part or portion near the pelvis is 

 paler and shows bright red blood- 

 vessels. The outer part is called 

 the cortex, and the part between 

 this and the pelvis is called the 

 medulla. Notice that the small 

 blood-vessels of the medulla ap- 

 pear to radiate from the cortex 

 towards the pelvis, being best seen 

 close tothe cortex. This is because 

 v.a, Small artery entering and forming the main arteries which have come 



the glomerulus^/, and finally leav- j nt() the kidney at the hilus go to 

 ing in a small vein, v'.c ; r, tubule ; . . , 



a, epithelium over the glomerulus; the re 1On DCtWCen the medulla 



b, epithelium lining the capsule. and the cortex and there break 



up into fine branches, which run 



on the one side into the medulla, where they can be distinctly 

 seen because they lie nearly parallel to one another, and on 

 the other side into the cortex, where they are not well seen 

 because they run in a very irregular way. These vessels lie 

 between the tubules which form the substance of the kidney. 

 Traced back from their openings in the pelvis, the tubules 

 can be seen by the microscope to lie parallel to one another in 

 the medulla, and to greatly increase their number by*branching. 

 At the limit of the medulla the tubules pass on into the cortex, 

 where they at once take a very irregular and tortuous course, 



FIG. 74. A Malpighian capsule. 



