CHAPTER XIV. 



THE KIDNEY. 



IF a longitudinal section be made through the 

 middle of a rabbit's kidney, the cut surface will pre- 

 sent a well-marked separation into an outer cortical 

 and an inner medullary substance ; between these 

 two are seen sections of large blood-vessels. The 

 medullary portion, called me dii liar y pyramid or me- 

 dulla, and occupying the central part of the organ, 

 terminates in the pelvis in a single short, rounded 

 prolongation, called the papilla, at the end of which, 

 with a low magnifying power, several tiny openings 

 may be seen. The cut surface of the papilla pre- 

 sents an uniform grayish appearance, while the seg- 

 ment of the medulla adjacent to the cortex presents 

 distinct bands or striae, radiating from the papilla 

 and extending, in the form of narrow, isolated 

 tapering rays, into the cortex, almost to the surface 

 of the organ ; these cortical rays are called medullary 

 rays. 



The cortex, surrounding the medulla like a thick 

 shell, and covered by a firm, dense layer of connec- 

 tive tissue the capsule consists, besides the medul- 

 lary rays, of a grayish substance lying in the form 



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