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HANDBOOK OF PHYSIOLOGY. 



hedral cells. (8) About midway in the boundary layer the tube again 

 narrows, forming the ascending spiral of Henle's loop, but is still lined, 

 with polyhedral cells. At the point where the tube enters the cortex (9) 

 the ascending limb narrows, but the diameter 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 imbricated cells. The tube next 

 becomes convoluted (11), forming the distal convoluted tube or intercal- 

 ated section of Schweigger-Seidel, which is identical in all respects with the 

 proximal convoluted tube (12 and 13). The curved and straight collect- 



FIG. 245. From a vertical section through the kidney of a dog the capsule of which is supposed 

 to be on the right. ^ The capillaries of the Malpighian corpuscle -viz., the glomerulus, are arrang- 

 ed in lobules; j&fneck of capsule; c, convoluted tubes cut in various directions; &, irregular tubule; 

 d, e, and/, are 1 straight tubes running towards capsules forming a so-called medullary ray, d, col- 

 lecting tube; e, spiral tube ; /, narrow section of ascending: limb, x 380. (Klein and Noble Smith.) 



ing tubes, the former entering the latter at right angles, and the latter 

 passing vertically downwards, 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 papillary layer, 

 and, joining with other collecting tubes, forms 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). 



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 intra-nu- 



