ADVANCED PHYSIOLOGY 



Medulla 



Cortex 



Ureter 



of numerous tubules, which come from the outer layer of the 

 kidney, the cortex. The outer ends of the tubules are the real 

 glands, which produce the kidney secretion; their inner ends 



drain these glands, 

 carrying their secre- 

 tion to the pyramids 

 and pouring it into 

 the funnel-like open- 

 ing of the ureter, 

 whence it runs to the 

 bladder. To under- 

 stand the structure 

 and action of the kid- 

 neys we must study 

 these tubules more 

 minutely. 



A Urinary Tubule. 

 In Figure 110 a dia- 

 gram of the arrange- 

 ment of two urinary 

 tubules is given. Each 

 begins at its outer 

 end, i.e. the end to- 

 ward the kidney surface, in the form of a bulb-like expansion, the 

 walls of which are only one cell thick. This bulb, the Malpighian 

 capsule, is deeply indented on one side, so as to form a pocket. 

 From this pocket, there arises a long tube which takes a some- 

 what irregular course. It turns toward the center of the kidney, 

 but almost at once becomes twisted into irregular coils, 

 called the convoluted part of the tube. Afterwards, it pro- 

 ceeds in a fairly straight line toward the pelvis of the kidney, 

 but goes only a short way, when it turns sharply on itself and 

 returns toward the outer surface of the kidney once more, 

 near where it started. Here it is joined by other tubules of 

 the same sort and together the united tubes now pass as 



FIG. 



109. REPRESENTING A KIDNEY OPENED 

 LENGTHWISE 



(Sappey) 



