EXCEETION BY THE KIDNEY. 



The kidney in man and other mammals may be described as 

 a very complex arrangement of tubes lined with many differ- 

 ent forms of secreting cells, surrounded by a great meshwork of 

 capillaries, bound together by connective tissue, the quantity 



Fia. 815.— Vertical longitudinal section of horse's kidney (Chanveau). o, cortical por- 

 tion; J, mednllary portion; c, peripheral portion of latter; d, interior of pelvis; 

 d', d', arms of pelvis; e, horder of crest; /, infundibuliim; g, ureter. 



varying with the animal, and the whole inclosed in a capsule. 

 The organ is well supplied with lymphatics and nerves. 

 Though the tubes are so complex, the kidney may be divided 

 into zones which contain .mostly but one kind of tubule. 



Among vertebrates, till the reptiles are reached, the kidney 

 is a persistent Wolffian body, hence its more simple form. 



In most fishes the kidney is a very elongated organ, though 



