THE URINARY APPARATUS. 



573 



substances, and among those distributed to the cortical are some regularly 

 disposed, which furnish, on each side, the glomerule ramifications ; these are the 

 afferpnt vessels, or Maljdf/hian glomeruhs (or tuft.-<) •, the others form a polyhedral 

 plexus around the convoluted tubes and corjiora Malpighiana. The efferent I'essels 

 of the renal glomerules enter this plexus. 



The arterial branches of the medullary substance descend between and 

 parallel with the straight tubes (to form the arteriole redce), and anastomose by 

 transverse branches, so as to form a network with elongated meshes (around and 

 between the tubuli). 



The {renal vein) issues from the kidney by the hilus, and succeeds the arterial 



Fig. 341. 



Fig. 342. 



mSTRIBDTION OF THE RENAL VESSELS IN THE 

 horse's KID.N'EY. 



a, Branch of renal artery ; af, atferent vessel ; 

 m, m, malpighian tufts; cf. cf, efferent 

 vessels; p, vascular plexus surrounding the 

 tubes ; si. straight tube ; ct, convoluted tube. 



capillaries. In the medullary substance, 

 there are straight veins as there are straight 

 arteries. On the surface of the organ, 

 beneath the fibrous envelope, are the stellate 

 veins of Verheyen — the junction of five or 

 six venules which converge towards a 

 central vein. The venules of the two 

 portions 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 attributed. 



b. The lymphatiis are abundant in tlie mass, but rare at the superficies of 

 the organ ; they form plexuses, the ultimate branches of which pass to the 

 sublumbar glands. 



c. The nerves emanate from the solar })lexm, and form a particular network 

 around the arteries, exhibiting, on their course, some microscopic ganglia. It is 

 not known how they terminate. 



Development, — The kidneys appear veiy early in the fcEtus, above and a 

 39 



diagram of the course of the urini- 

 ferous tubule. 



a, Orifice of tubule at pelvic crest; 6, re- 

 current branches which form loops, c, in 

 the medullary portion of the kidney, and 

 terminate in the Malpighian capsules in 

 the cortical portion. 



