THE URINARY ORGANS. 



167 



ries run, for the most part, parallel to the renal tubules, with com- 

 paratively few transverse anastomosing branches. For this reason 

 they have been called the "vasa recta." They also receive blood 

 from little twigs given oft" from the arterial arcade. 



The blood from the intertubular capillaries is collected in veins, 

 which run a course parallel to that of the arteries and lie in close 

 proximity to them. They have received names similar to those of 

 the corresponding arteries : " interlobular veins," " venae recta?," 

 and " venous arcade." Relatively large veins also leave the kidney 

 from beneath the capsule on the convex surface of the organ. They 

 are called the " stellate veins." 



The Malpighian body is enclosed by a thin fibrous capsule 

 (Bowman's capsule), which is perforated at two opposite points to 

 permit the passage on the one hand of the afferent and efferent 

 vessels, and on the other hand to allow of a communication between 

 its cavity and the beginning of the uriniferous tubule. When dis- 

 tended with blood the glomerulus nearly fills this capsule, but when 

 collapsed it is retracted toward the attachment formed by the ves- 

 sels that pierce the capsule. It is covered by a single layer of epi- 



Fig. 143. 



Fig. 144. 



mwmmmm 



Cross-sections of convoluted tubules lined with cells in different states of activity. (Disse.) 



Fig. 135.— From a criminal directly after execution. Cells in a state of rest. The cells are 

 low and granular, and present a striation of their free ends resembling cilia. 



Fig. 136. — From a cat. The cells are enlarged, because charged with material to be excreted, 

 and the striated border is nearly obliterated. Similar appearances have been observed 

 in the human kidney. In one of the lower cells in this figure a faint striation of the 

 attached end is just discernible. This increases in distinctness as the cell becomes sur- 

 charged with excretory material, when the more central portion of the cytoplasm 

 becomes hyaline and contains the nucleus. 



thelial cells, which is reflected at that attachment and forms a lining 

 for the inner surface of the capsule to the point where its cavity 

 opens into the lumen of the renal tubule. Here the epithelial lining 

 becomes continuous with that of the tubule (Fig. 142). 



The different portions of the uriniferous tubule differ in their 



