MINUTE STRUCTURE OF KIDNEY. 163 



back to the bladder. Find also the renal artery and vein, 

 branching as they enter the kidney through the hilum. 



3. With a sharp knife split the kidney like a bean, begin- 

 ning at the outer border, stopping the cut when the cavity, 

 lined by a white membrane, is reached near the hilum. With 

 forceps pry about to explore the cavity bounded by this white 

 membrane. Note the branches of the cavity into the kidney. 

 Note also the extension of the white membrane into these 

 cavities. Make out that the blood vessels extend through 

 these white branches to the outer part of the kidney. Count 

 these branches. 



4. In the center of the white membrane find the opening 

 of the ureter, through which the urine is conveyed to the 

 bladder. Pass a probe through this opening into the ureter. 



5. Note the difference in color of the outer and inner 

 parts of the kidney. At the line of change of color find 

 where the blood tubes first branch into the real kidney sub- 

 stance. Examine carefully the cut surface of the kidney, to 

 see its markings. 



6. Make a drawing of one-half of the kidney as seen from 

 the inside, showing the above points. 



7. Cut across the middle of the kidney at right angles to 

 its length, and make a drawing of the cross-section. The pro- 

 jection of the kidney substance into the cavity opposite the 

 ureter is the Urinary Pyramid, and from its apex, through 

 many fine holes, issues the urine which the kidney has 

 secreted from the blood. 



Microscopic Structure of the Kidney. If microscopic 

 sections of the kidney are at hand they should be examined ; 

 but the kidney is so complicated in structure that a diagram 

 is needed in connection with the sections and the descriptions. 

 The unit of structure in the kidney is a tube which takes 

 material from adjacent blood capillaries. The relation of the 



