EXCRETION AND THE EXCRETORY ORGANS 



521 



inner or medullary. The medullary portion is less red and more 

 glistening to the eye, is finely striated in a radial direction, and 

 does not consist of one continuous mass but of a number of con- 

 ical portions, the pyramids of Malpighi, 2', each of which is sep- 

 arated from its neighbors by an inward prolongation, 4, of the 



,6 

 2' 



FIG. 139. Section through the right kidney from its outer to its inner border, 

 1, cortex; 2, medulla; 2', pyramid of Malpighi; 2", pyramid of Ferrein; 5, small 

 branches of the renal artery entering between the pyramids; A, a branch of the 

 renal artery; D, the pelvis of the kidney; U, ureter; C, a calyx. 



cortical substance: this, however, does not reach to the inner end 

 of the pyramid, which projects, as the papilla, into a calyx of the 

 ureter. At its outer end each pyramid separates into smaller 

 portions, the pyramids of Ferrein, 2", separated by thin layers of 

 cortex and gradually spreading everywhere into the latter. The 

 cortical substance is redder and more granular looking and less 



