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A MANUAL OF PHYSIOLOGY 



go, until at length they open as ducts of Bellini on the apex of a 

 papilla. The two convoluted tubules (with the spiral and zigzag 

 tubules) are lined by similar epithelial cells with granular contents, 

 and the tendency of the granules to be arranged in rows perpen- 

 dicular to the basement membrane gives them a striated or ' rodded ' 

 appearance (Fig. 173). The granules are eosinophile (p. 17), which 

 is also a character of the granules of other secreting cells. Towards 

 the lumen the cells may show a brush of processes, looking like 

 cilia, but in mammals these are not motile. The ascending part 

 of Henle's loop also has cells of the same general character, with 



i 



I 



I 



i 



FIG. 173. FROM A VERTICAL SECTION OF DOG'S KIDNEY TO SHOW THE STRUC- 

 TURE OF DIFFERENT PORTIONS OF THE RENAL TUBULE (KLEIN). 



a, Bowman's capsule enclosing glomerulus, the capillaries of which are arranged 

 in lobules separated by a little connective tissue. The capsule and glomerulus 

 together constitute a Malpighian body or corpuscle ; n, neck of capsule ; c, c, con- 

 voluted tubules, cut in various directions ; b, irregular or zigzag tubule ; d, e, and 

 / are straight tubules, which take part in the formation of a medullary ray or 

 pyramid of Ferrein ; d, collecting tubule ; e, e, spiral tubule ; /, narrow part of 

 ascending limb of Henle's loop-tubule ; b, c, and e are lined with rodded epithelium. 



numerous granules, although the ' rodding ' may not be so distinct. 

 We shall see directly that the morphological resemblance is the index 

 of a functional likeness. The blood-supply of the tubules, especi- 

 ally of the convoluted portions, is exceedingly rich, the efferent 

 vessels of the glomeruli breaking up around them into a close- 

 meshed network of capillaries, from which the blood is collected 

 into interlobular veins running parallel to the interlobular arteries 

 between the pyramids of Ferrein. The straight tubules of the 

 medulla are also surrounded by capillaries given off from straight 

 arteries (arteriae rectae) running down into it partly from the arterial 

 arches and partly from efferent vessels of the glomeruli nearest the 



