KATABOLISM. 



427 



effectually prevents regurgitation. The secretion of the 

 kidneys drips, little by little, continually. It accumu- 

 lates in the bladder, and is thence from time to time 

 voided through the urethra. 



Pelvis of the Kidney.— If the ureter be cut away, 

 we expose a deep concavity called the pelvis. Its whole 

 interior is covered with 

 mammillary protuber- 

 ances, like the ends of 

 the fingers put together. 

 These are the ends of 

 the cones. In the living 

 animal (chloroformed) 

 we may see liquid oozing 

 from innumerable pores 

 on this surface, collect 

 into drops, and run 

 down. These pores are 

 the openings of the uri- 

 niferous tubules. 



Section. — By longi- 

 tudinal section through 

 the pelvis (Fig. 297) it 

 is at once seen that there 

 are two parts of the kid- 

 ney, differing in color 

 and structure — an inner 

 portion, of lighter color 



and radiated structure, and an outer portion, darker and 

 nonradiated. The former is the medullary and the latter 

 the cortical portion. The excretion takes place mainly 

 in the cortical portion ; the medullary mainly transmits 

 it to the pelvis. 



Minute Structure. — Examined with a microscope, 

 the medullary portion is seen to consist of straight 



Fig. 297. — Section of the kidney showing 

 structure : P, pelvis ; «, ureter ; m, 

 medullary, and c, cortical portion ; a a, 

 arteries. 



