THE KIDNEYS AND URINE. 



351 



ter varies considerably; here and there the cells are more flattened, but 

 both in this as in (8) the cells are in many places very angular, branched, 

 and imbricated. It then joins (10) the "irregular tubule" which has a 

 very irregular and angular outline, and is lined with angular and imbri- 

 cated cells. The tube next becomes convoluted, (11) forming the dixfal 

 convoluted tube or intercalated section of Schiveigger-Seidel, which is 

 identical in all respects with the proximal convoluted tube (12 and 13). 

 The curved and straight collecting tubes, the former entering the latter 

 at right angles, and the latter passing vertically downward, are lined with 

 polyhedral, or spindle-shaped, or flattened, or angular cells. The straight 

 collecting tube now enters the boundary layer (14), and passes on to the 



OTfc 



FIG. 242. 



FIG. 243. 



FIG. 242. Transverse section of a renal papilla; a, larger tubes or papillary ducts: 6, smaller 

 tubes of Henle: c, blood-vessels, distinguished by their flatter epithelium; d, nuclei of the stroma. 

 (Kolliker.) x 300. 



FIG. 243. Diagram showing the relation of the Malpighian body to the uriniferous ducts and 

 blood-vessels, a, one of the interlobular arteries; a', afferent artery passing into the glomerulus; c, 

 capsule of the Malpighian body, forming the termination of and continuous with t, the uriniferous 

 tube; e', e', efferent vessels which subdivide in the plexus jp, surrounding the tube, and finally ter- 

 minate in the branch of the renal vein e (after Bowman). 



papillary layer, and, joining with other collecting tuoes, form larger 

 tubes, which finally open at the apex of the papilla. These collecting 

 tubes are lined with transparent nucleated columnar or cubical cells (14, 

 15, 16). 



The cells of the tubules with the exception of Henle's loop and all 

 parts of the collecting tubules, are, as a rule, possessed of the mtra-nuclear 

 as well as of the intra-cellular network of fibres, of which the vertical rods 

 are most conspicuous parts. 



Heidenhain observed that indigo-sulphate of sodium, and other pig- 

 ments injected into the jugular vein of an animal, were apparently ex- 

 creted by the cells which possessed these rods, and therefore concluded 

 that the pigment passes through the cells, rods, and nucleus themselves. 



