442 



CHAPTEE XY. 



THE KIDNEYS AND THEIR SECRETION. 



Structure of the Kidneys. 



THE kidney is covered on the outside by a rather tough 

 fibrous capsule, which is slightly attached by its inner sur- 

 face to the proper substance of the organ by means of very 

 fine fibres of areolar tissue and minute blood-vessels. 

 From the healthy kidney, therefore, it may be easily torn 

 off without injury to the subjacent cortical portion of the 

 Fig. 113.* organ. At the hilus or 



notch of the kidney, it 

 becomes continuous with 

 the external coat of the 

 upper and dilated part of 

 the ureter. 



On making a eection 

 length-wise through the 

 kidney (fig. 113) the main 

 part of its substance is 

 seen to be composed of 

 " two chief portions, called 

 respectively the cortical 

 and the medullary portion, 

 the latter being also some 

 times called the pyramidal 

 portion, from the fact of its being composed of about a 



* Fig. 113. Plan of a longitudinal section through the pelvis and 

 substance of the right kidney, \ ; a, the cortical substance ; b, b, broad 

 part of the pyramids of Malpighi ; c, c, the divisions of the pelvis 

 named calyces, laid open ; c', one of these unopened ; d, summit of the 

 pyramids or papillae projecting into calyces ; e, e, section of the narrow 

 part of two pyramids near the calyces ; p, pelvis or enlarged divisions 

 of the ureter within the kidney ; , the ureter ; s, the sinus ; h, the 

 hilus. 



