Chap, xxx.] KIDNEY, URETER, AND BLADDER'. 235 



of nucleated epithelial cells, polyhedral, or even 

 columnar in the young, squamous in the adult state. 

 The membrana propria and epithelium dip in, of 

 course, between the lobules of the glomerulus, and 

 represent in reality the visceral layer of the capsule 

 of the Malpighian corpuscle, the capsule of Bowman 

 being the parietal layer. The glomerulus is connected 

 at one pole with an afferent and efferent arterial 

 vessel, the former being the larger. 



Between Bowman's capsule and the glomerulus 

 there is a space, the size of which differs according 

 to the state of secretion, being chiefly dependent on 

 the amount of fluid present. 



The Malpighian corpuscles are distributed in the 

 labyrinth of the cortex only, with the exception of a 

 thin peripheral layer near the outer capsule, and a 

 still thinner layer near the boundary layer. The 

 Malpighian corpuscles near the boundary layer are the 

 largest, those near the periphery the smallest; in 

 the human kidney their mean diameter is about j-|^ 

 of an inch. 



306. (2) On the side opposite to that where the 

 afferent and efferent arterioles join the glomerulus, 

 the capsule of Bowman passes through a narrow neck 

 into the cylindrical urinary tubule in such a way, 

 that the membrana propria and epithelium of the 

 capsule are continued as the membrana propria and 

 lining epithelium of the tubule respectively, and 

 the space between the capsule of Bowman and 

 the glomerulus becomes the cavity or lumen of the 

 urinary tubule. 



307. (3) After it has passed the neck, the urinary 

 tubule becomes convoluted ; this is the proximal con- 

 voluted tubule (Fig. 133). It is of considerable length 

 and is situated in the labyrinth. It has a distinct 

 lumen, and its epithelium is a single layer of polyhedral 

 or short, columnar, angular, or club-shaped cells, each 



