STRUCTURE OF THE KIDNEY 



165 



blood-vessels, the dilated commencement of the tubule being known 

 as the capsule (fig. 200, i ). The tubule leaves the capsule by a nar- 

 row neck (a) ; it is at first convoluted (first convoluted tubule, s), but 



FIG. 200. DIAGRAM OF THE COURSE OF TWO URINI FERGUS TUBULES. 



A, cortex ; B, boundary zone ; c, papillary zone or the medulla ; a, a', superficial and deep 

 layers of cortex, free from glomeruli. For the explanation of the numerals, see the text. 



soon becomes nearly straight or slightly spiral only (spiral tubule, 4), 

 and then, rapidly narrowing, passes down into the medulla towards the 

 dilated commencement of the ureter as the descending tubule of Henle 

 (5). It does not at once, however, open into the pelvis of the kidney, 



