86 ZOOLOGY. 



cavity called calyx (c), and whose base, directed outwards, is, 

 as it were, encased in the cortical substance of the kidney, 

 formed out of the mass constituted by that portion of the 

 tubes which is massed into heaps rolled on each other ; the 

 other part is called tubular or medullary ; being the part formed 

 by the fasciculi themselves. In the 

 young, and in many animals throughout 

 life, such as the bear and otter, these 

 pyramids remain distinct, and each 

 kidney is then composed of several 

 separate lobes ; but generally they unite 

 together, and the calyces, which are but 

 excrementory tubes, unite to form a 

 pelvis or general reservoir, from which 

 proceeds the ureter (Fig. 61 d). A. great 

 number of bloodvessels creep between 

 these secreting tubes, and constitute, in 

 g. 2.-Urinary the cortical portion of the gland, a very 

 Apparatus.* close network, in the midst of which may 

 be seen certain spherical bodies, formed 

 also of bloodvessels collected into bunches in the interior of 

 the ampulla already mentioned. 



The urine is formed in the cortical part of the kidneys. 

 It descends by the tubular part into the calyces, and thence 

 into the pelvis of the kidney; this terminates in the ureter 

 (Fig. 62 5), by which the urine descends to the bladder. This 

 latter organ is situated in the pelvis and behind the os pubis. 

 It is formed internally by a mucous membrane ; externally, 

 by a muscular and cellular layer. The peritoneum also par- 

 tially invests it, and gives it support. Inferiorly it terminates 

 in the canal of the urethra, by which the urine escapes from 

 the body. 



163. The urine is a yellowish acid liquid, which in 

 man, in the normal state, is composed of 93 parts water, 

 3 of a peculiar substance called urea ; a very small portion 

 of uric acid, lactic acid, various salts, as muriate of soda, 

 alkaline sulphates, phosphate of lime, &c., make up the 100 

 parts. 



In carnivorous mammals the urine resembles that of man, 

 but the uric acid is wanting. In herbivorous mammals, the 

 urine is alkaline, and a peculiar substance is found, the hip- 



* a, the kidneys ; 5, the ureter ; e, the bladder ; d, canal of the urethra. 



