THE KIDNEYS. 



489 



Fig. 251. 



between the corpora and convoluted tubes, the other affording a passage 

 to the afferent and efferent vessels of the glomerule. 



3. VESSELS AND NERVES. a. The kidney pos- 

 sesses a special artery and vein, remarkable for 

 their enormous volume. 



The artery forms several branches which reach 

 the kidney by its inner border and inferior face, 

 and divide into a certain number of principal 

 vessels, which are disposed in a wavy manner on the 

 limits of the cortical and medullary substances. 

 From them are given off branches to each of 

 these substances, and among those distributed to 

 the cortical are some regularly disposed, which 

 furnish, on each side, the glomerule ramifications ; 

 these are the afferent vessels or Malpighian glome- 

 rules (or tufts) ; the others form a polyhedral 

 plexus around the convoluted tubes and corpora 

 Malpighiana. The afferent vessels of the renal 

 glomerules enter this plexus. 



The arterial branches of the medullary sub- 

 stance descend parallel to the straight tubes, and 

 anastomose by transverse branches, so as to form 

 a network with elongated meshes. 



The vein issues from the kidney by the hilus, 

 and succeeds the arterial capillaries. In the me- 

 dullary substance, there are straight veins as there 

 are straight arteries. On the surface of the organ, 

 beneath the fibrous envelope, are the stars of 

 Verheyen : the junction of five or six venules which converge towards a 

 central vein. The veinletsof the . 52 



two substances collect into more 

 voluminous vessels, which form 

 complete arches at their limits ; 

 it is to the presence of these 

 vascular canals, that the dark 

 colour observed at this point of 

 the renal tissue must be attri- 

 buted. 



6. The lymphatics are abund- 

 ant at the superficies and in the 

 mass of the organ, forming plex- 

 uses, whose ultimate branches 

 pass to the sublumbar glands. 



c. The nerves emanate from 

 the solar plexus, and compose a 

 particular network around the 

 arteries, exhibiting, on their 

 course, some microscopic gan- 

 glia. It is not known how they 

 terminate. 



DEVELOPMENT. The kidneys appear very early in the foetus, above and a 

 little behind the Wolffian bodies. They are then very distinctly lobulated, but 

 the lobes gradually become fused, and have entirely disappeared at birth ; the 



DISTRIBUTION OF THE RENAL 

 VESSELS IN THE HORSED 

 KIDNEY. 



a, Branch of renal artery ; a/, 

 Afferent vessel ; m, m, Mal- 

 pighian tufts ; ef, ef, Ef- 

 ferent vessels ; p, Vascular 

 plexus surrounding the 

 tubes ; s, Straight tube ; 

 ct, Convoluted tube. 



TRANSVERSE SECTION OF THE KIDNEY. 



Inferior border ; 2, Cortical tissue ; 3, Section of 

 blood-vessels ; 4, Pelvis ; 5, Ureter ; 6, Superior 

 border; 7, Renal artery; 8, Proper capsule. 



