132 NOKMAL HISTOLOGY. 



the kidney occupies the outer one-third and contains the labyrinth, 

 medullary rays, and blood-vessels. The labyrinth comprises the Mal- 

 pighian bodies and uriniferons tubules. The Malpighian body con- 

 sists of the capsule of Bowman and the glomerulus. The capsule 

 is lined with a single layer of flattened epithelial cells. The glom- 

 erulus consists of a coil of capillaries. Entering each capsule is an 

 afferent artery, and passing from it an efferent vein. The urinif- 

 erous tubule, which proceeds from the pole of the capsule opposite 

 the entrance of the artery, comprises the following parts : (1) The 

 neck, lined with low cuboidal cells; (2) the convoluted tubule, 

 which is lined with low columnar cells ; (3) the spiral tubule, similar 

 in structure to the convoluted portion; (4) the descending limb of 

 Henle's loop, lined with simple squamous epithelium; (5) Henle's 

 loop, composed of polyhedral cells with flattened nuclei; (6) the 

 ascending limb of Henle's loop, with structure resembling that of 

 the loop; (7) the irregular tubule, composed of striated epithe- 

 lium; (8) the distal convoluted tubule, consisting of granular 

 epithelium; (9) the arched collecting tubule, lined with low cu- 

 boidal cells; (10) the straight collecting tubule, which possesses 

 columnar cells; (11) the excretory duct, or tube of Bellini, which 

 is lined with tall columnar epithelial cells. 



The columns of Bertini constitute the masses of the kidney be- 

 tween the Malpighian pyramids; they extend to the pelvis. 



The medullary rays are tapering bundles of straight tubules, 

 which extend from the medulla into the cortex. 



The blood-vessels of the kidney enter at the hilum. The renal 

 artery passes through the sinus, gives off twigs, which extend 

 through the columns of Bertini to the cortex, and enters the Mal- 

 pighian body by the afferent artery, which splits up into capillaries 

 to form the glomerulus ; these unite to form the efferent vein, which 

 unites with similar veins to form the interlobular vein. 



The stroma constitutes the connective tissue structures, which in- 

 vest the blood-vessels and tubules. 



The medulla is composed of from eight to twenty Malpighian pyr- 

 amids. Each pyramid is made up of tubules, its base corresponding 

 with the line of juncture between the medulla and cortex; and its 



