CHAP, in.] ELIMINATION OF WASTE PRODUCTS. 647 



These make their way from the sympathetic chain, into which 

 they first pass either by joining the splanchnic nerves low down, 

 or by a more direct course, to the solar plexus, and thence to the 

 renal plexus. 



Nothing very definite is known of the termination of the renal 

 nerves within the kidney. Some of them, and considering how 

 vascular is the kidney, probably a large number, end in the blood 

 vessels; but some of them must have other endings. We have, 

 however, no evidence that any of them are connected with the 

 epithelium of the tubules. Since under abnormal circumstances 

 afferent impulses sufficient to give rise to very great pain may 

 pass up to the central nervous system from the kidney, at least 

 from the pelvis of the kidney, some of the fibres of the renal 

 nerves are afferent fibres ; and some of the medullated fibres are 

 probably of this nature. 



