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TEXT-BOOK OF PHYSIOLOGY 



the volume-changes exhibit not only the respiratory but also the cardiac 

 undulations. 



The Influence of the Nerve System. The influence of the nerve system 

 in regulating the blood-supply to the kidney is evident from the results of 

 experimentation. If the nerves which accompany the renal artery into the 

 kidney are divided, the artery at once dilates, the kidney enlarges, and a 

 copious flow of urine takes place. If the peripheral ends of these nerves be 

 stimulated with induced electric currents the artery contracts, the kidney 



FIG. 209. SCHEME OF A RENAL ONCOMETER OR PLETHYSMOGRAPH. K, kidney; RT, receiving 

 tambour or capsule; PB, pressure bottle; PR, recording piston. 



diminishes in size, and the flow of urine ceases. In addition to these vaso- 

 constrictor nerves, there is evidence that the kidney also receives vaso-dilata- 

 tor nerves. The vaso-constrictor nerves emerge from the spinal cord and are 

 found in the anterior roots of the eleventh, twelfth, and thirteenth dorsal 

 nerves, in the dog. Direct and reflex stimulation of the centers of origin 

 of these nerves gives rise to contraction or to a dilatation of the artery, a 

 diminution or a swelling of the kidney, and a decrease or an increase in 



FIG. 210. CURVE OF THE VARIATIONS IN THE VOLUME OF THE KIDNEY. 



secretion, independent of any variation in general blood-pressure according 

 to the nature of the cause acting. 



The route of the vaso-constrictor nerves is, in the dog at least, through 

 the lesser splanchnics, the terminal branches of which arborize around the cells 

 of the renal ganglia; from these ganglia new fibers arise which pass through 

 the renal plexus into the kidney to be distributed to the muscle coat of the 

 renal artery branches. Section of these nerves is followed by a dilatation 

 of the renal vessels and an increase in the flow of urine. Stimulation of the 



