264 NORMAL HISTOLOGY AND ORGANOGRAPHY. 



limb is larger but the epithelium takes on the char- 

 acteristic of the proximal convoluted tube, although 

 the cells are a little smaller and may contain pig- 

 ment granules. The ascending limb passes straight 

 up a medullary ray, from which it emerges to again 

 enter the cortex, where it becomes irregular in out- 

 line forming (6) the irregular tubule, which quickly 

 becomes much twisted and coiled to form (7) the 

 distal convoluted part. In the irregular part the cells 



are very un- 



Convoluted , . 



portions, equal in size 

 and a rod- 

 like struc- 

 ture of the 

 cytoplasm 

 is very dis- 

 tinct, while 

 the base- 

 ment mem- 

 brane is said 

 to be ab- 

 sent. The 

 cells of the 



apsule. 



Neck. 



Fig. 20 1. Section of a portion of the labyrinth of the 

 kidney cortex. 



distal convoluted tube are rather long, with a distinct 

 membrane and a highly refractive appearance of the 

 protoplasm. Near the basement membrane minute 

 projections from adjacent cells may be seen to inter- 

 lock. Finally, this portion terminates in (8) a 

 short functional tubule, which leaves the cortex and 

 enters a medullary ray to join the last part (9), the 

 collecting tubule. The latter passes straight through 

 the Malpighian pyramid to open on its surface in a 

 small pore. In its course the collecting tube receives 



