344 



TEE URINARY SYSTEM 



at first with extreme convolutions, but later pursuing a rather 

 spiral course (spiral tubule of Schachowa). On reaching the bor- 

 der of the medulla the tubule becomes sharply constricted and 

 enters the medullary boundary zone at the thin descending limb 

 of Henle's loop. 



N, 



e d g 



FIG. 283. FROM THE CORTEX OF THE HUMAN KIDNEY, SHOWING A TRANSECTION OF A 



MEDULLARY RAY IN THE LOWER LEFT-HAND CORNER. 



a, glomerulus ; J, capsule of Bowman ; c, proximal convoluted tubule ; d, collecting 

 tubule ; e, ascending limb .of Henle's tubule ; /, spiral tubule ; <7, blood vessel. Hema- 

 toxylin. x 200. (After Schaper, from Stohr.) . 



The epithelium of the convoluted tubule is of the columnar 

 or pyramidal type, its cells having broad, firmly united bases and 

 conical free apices. The lateral margins of the cells are often so 

 intimately blended at the base as to resemble a syncytium. When 



