THE KIDNEYS 



991 



at all events, it is much more distinct in this situation, the nucleus, which appears 

 flattened and angular, being still situated near the lumen (Fig. 547, D). In the 

 irregular tubule the cells undergo a still farther change, becoming very angular, 

 and presenting thick bright rods or markings, which render the striation much 

 more distinct than in any other section of the urinary tubules (Fig. 547, H). In 



FIG. 723. Transverse section of pyramidal substance of kidney of pig, the blood-vessels of which are injected, 

 a. Large collecting tube cut across, lined with cylindrical epithelium, b. Branch of collecting tube cut across, 

 lined with epithelium with shorter cylinders, c and d. Henle's loops cut across, e. Blood-vessels cut across. 

 D. Connective-tissue ground-substance. 



the distal convoluted tubule the epithelium appears to be somewhat similar to that 

 which has been described as existing in the proximal convoluted tubule, but 

 presents a peculiar refractive appearance (Fig. 547, B). In the curved tubule, just 

 before its entrance into the straight collecting tube, the epithelium varies greatly 



a A 



1 n,. Vil. Diagrammatical sketch of the blood- FIG. 5o2. A portion of Fig. 551 enlarged. (The 



voM'ls of kidney. references are the same.) 



A, . Proper renal artery and vein, the former giving off the renal afferents, the latter receiving the renal 

 efferents. B, b. Interlobular artery and vein, the latter commencing from the stellate veins, and receiving 

 branches from the plexus around the tubuli contorti.the former giving off renal afferents. c. Straight tube, sur- 

 rounded by tubuli contort!, with which it communicates, as more fully shown in Fig. 544. D. Margin of medul- 

 lary substance. E, E, K. Receiving tubes cut off. F,/. Arteriolse et venae recta;, the latter arising from (G) the 

 plexus at the medullary apex. 



as regards the shape of the cells, some being angular with short processes, others 

 spindle-shaped, others polyhedral (Fig. 547, E). 



In the straight tubes the epithelium is more or less columnar ; in its papillary 

 portion the cells are distinctly columnar and transparent (Figs. 549, 550), but as 

 the tube approaches the cortex the cells are less uniform in shape ; some are 

 polyhedral, and others angular with short processes (Fig. 547, F and G). 



