CHAPTER XXII. 

 URINAEY EXCKETION. 



THE urine is the most important fluid excretion, for by it, in 

 mammalia, nearly all the nitrogen of the used-up proteid leaves 



FIG. 170. 



Section of Kidney of Man. a. Cortical substance composed chiefly of con- 

 voluted tubules ; the portions between the medullary pyramids form the 

 columns of Bertin (e). b. Pyramids of medullary substance, composed of 

 straight tubes, etc., radiating towards cortex, to form the pyramids of Ferrein. 

 d. Commencement of ureter leading from central sac or pelvis, c. Papillae 

 where the tubes open into pelvis. (Cadiat.) 



the body in the form of urea. The construction of the urinary 

 glands requires the special notice of the physiologist. 



