FIG. 1607. 



Vein 



,882 HUMAN ANATOMY. 



on gaining the Malpighian corpuscle the ascending limb crosses the neck in close proximity to 

 th.-'glomerulns. with which it is connected by twigs from the vas efferens (Hamburger'), and 

 then an lies over the corpuscle to end in the succeeding convoluted tubule. The position of 

 the sudden transition in .in the narrow into the wider tube of Henle's loop vanes, the change 

 -tion.illy , curring alter the turn is reached, sometimes within the loop itself, but most Ire- 

 qnentlv within the descending limb a short distance above the loop. 



5. The Distal Convoluted Tubule. On gaining the level of the corresponding Malpighian 

 body the ascending limb gradually widens into the distal convoluted or intermediate tubule, a 

 canal' approximating tin- diameter (.O4o-.o45nnx) of the surrounding convoluted tubules, but 

 littering from the latter in its wider lumen and in the character of its epithelium. This consists 

 .)t well-defined culn.idal cells, with spherical nuclei, the cytoplasm of which, while granular, is 



comparatively clear and devoid of stria- 

 tions. The moderately tortuous path of 

 the intermediate tubule is marked by a 

 number of abrupt changes in direction, 

 but in general lies for a time enclosed by 

 the arch described by the corresponding 

 convoluted segment ( Schweiger-Seide! ), 

 which it finally crosses (Huber). 



6. The Connecting Tubule. This 

 portion of the tubule ( .023-. 025 mm. in 

 diameter) resembles the preceding seg- 

 ment in its clear epithelium, the lining 

 cells, however, being lower, with a cor- 

 responding increased lumen. After a 

 short and usually arched course, the con- 

 necting tubule enters the medullary ray 

 and, uniting with similar canals, joins in 

 forming the collecting tubule. 



7. The Collecting Tubule. This 

 first lies within the medullary ray, where 

 it forms the beginning of the system of 

 straight duct-tubes that culminates in 

 the canals opening upon the papilla, 

 and then passes into the renal pyramid. 

 During their course through the medul- 

 lary ray the collecting tubules repeatedly 

 unite to produce stems, which, while in- 

 creasing four- or fivefold in diameter, are 

 diminishing in number. In consequence 

 of this fusion within the pyramid, the col- 

 lecting tubules are disposed in groups 

 (Fig. 1609), each of which corresjxMids 

 to the tubules prolonged from a single 

 medullary ray and is surrounded by the 

 limbs of the loops of Henle. On enter- 

 ing the renal pyramid, the groups of col- 

 lecting tubules at first are separated by 

 the intervening bundles of straight blood- 

 vessels (vasa recta"} that are given off 

 from the larger twigs within the boun- 

 dary zone for the supply of the medulla. 



After passing to within alxmt 5 mm. of the apex of the papilla, towards which they converge, 

 the large < olle. ting , .mals undergo repeated junction, increasing in diameter but rapidly dimin- 

 ishing in nnmlM-r. to torm the wide papillary ducts. The epithelium lining the collecting tubules 

 ill.- l.itg.-r as well as tin- smaller consists of clear cuboidal or low columnar cells, sharply 

 defined from .,ne .mother and provided with spherical nuclei. The light-colored cytoplasm 

 and distinct demarcation of these elements render the collecting tubules conspicuous and their 



\ The Papillary Ducts. These, the final segments of the kidney tubules, number from 



ten to eighteen lot each single papilla, at the apex of which they end. Kach is formed by the 

 junction ot tiom t.n to thim of the larger collecting tubules (.o5o-.o6o mm.) and attains a 

 diameter of from _> -, mm The lining epithelium is composed of conspicuous, clear columnar 

 cells, alw.ut ...?. mm. in height and one-third as much in width, which rest upon a distinct 



Archiv f. Anat. u. Kntuick., Suppl. lid., 1890. 



Collecting 

 tubule 



M-i-ti.ui ..I renal medulla, showing Henle's 

 loops and collecting tubules. X 45- 



