Fig. 167. — Diagram of the STnucTURE of a Lobe of the Kidney. The lobe 

 is seen in vertical section, the cortex being marked off from the medulla. Four 

 medullary rays encroach upon the cortex. At the left is shown the course of a single, 

 continuous series of tubes — the straight and spiral tubes appearing in the medul- 

 lary ray, the straight, looped, and excretory in the medulla proper, the capsule, 

 neck, convoluted, irregular, and arched in the cortex proper. Next is seen the 

 lab>Tinth, composed of a mass of tubes in the cortex, with a medullary ray for a 

 centre. Equidistant from the ray on each side is a broken red line, marking the 

 position of an interlobular artery. The parts between these lines constitute a 

 lobule. Farther to the right is an interlobular artery, gi%'ing off lateral branches 

 (afferent vessels), each of which ends in a tuft of capillaries, from which the 

 blood is collected by an efferent vessel. The uppermost of the tufts is showti 

 enclosed in a capsule. On the right of the interlobular artery the efferent vessels 

 break up into a capillary network which surrounds the (unrepresented) tubes in the 

 cortex and ray. The lowest efferent sends vertical vessels also into the medulla. 

 On the right the interlobular vein is seen gathering the blood from all the parts sup- 

 plied by the interlobular artery. A branch of the renal artery courses upward be- 

 tween cortex and medulla, and forms an arch (here broken) over the base of the 

 medulla. From it the inttrlol)\ilar arteries pass upward into the cortex, and 

 straight branches go downward into the medulla, suppljing its structure, and end- 

 ing at the apex in the capillaries. From the last the radicles of the renal vein 

 arise, and accompany the straight arteries to the base of the medulla, where a %'e- 

 nous arch is formed, continuous with which is the vena comes of the entering artery. 

 The caljTC embraces the apex of the medullary pyramid. It is lined with epithe- 

 lium, which continues from it ov^er the apex, the latter being perforated with the 

 many apertures of excretory tubes. (Gerrish.) 



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