178 



ELEMENTARY PHYSIOLOGY 



LESS. 



project ; and their summits present multitudes of minute 

 openings — the final terminations of the tubules, of which 

 the thickness of the kidney is chiefly made up. If the 

 tubules be traced from their openings towards the outer 

 surface, they are found, at first, to lie parallel with one 

 another in bundles, which radiate towards the surface, 

 and subdivide as they go ; but at length they spread about 

 irregularly, and become coiled and interlaced. From this 



-SA. 



Fio. 51. — Longitudinal Section of the Human Kidney. 



Ct, the cortical substance ; M, the medullary substance ; P, the pelvis 

 of the kidney ; U, the ureter ; R.A, the renal artery ; Py, the pyramids. 



circumstance, the middle part, or medulla (medulla, 

 marrow) of the kidney looks different from the superficial 

 part or cortex {cortex, bark) ; but, in addition, the 

 cortical part is more abundantly supplied with vessels 

 than the medullary, and hence has a darker aspect. Each 

 tubule after a very devious course ultimately terminates 

 in a dilatation (Fig. 52) called a Malpighian capsule. 



