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THE EXCKETION OF UEINE 



449 



the 4th dorsal pair to the 4th lumbar (which correspond with the 

 second lumbar pair in man), contain vaso-constrictor fibres for the 

 kidney; but most of them run in the anterior roots of the llth, 

 12th, or 13th thoracic pairs. These vascular fibres, after passing 

 through the ganglia of the sympathetic chain, run to the solar plexus, 

 and thence to the renal plexus by the splanchnics, or other paths. 

 When the anterior roots of these spinal nerves are excited by 

 rhythmic excitation of low frequency, the result is not constriction 

 but active dilatation of the renal arteries, expressed in a swelling 

 of the kidney. This fact, discovered by Bradford, shows that 

 these roots contain vaso-dilator fibres to the renal arteries, besides 



FIG. 120. Increase of arterial pressure (P), and decrease in kidney volume (V), due to asphyxia 

 commencing at A. (J. Cohnheim and C. Roy.) 



the vaso-constrictors. The former are excited by rapid rhythmical 

 stimulation, the latter by a slow rhythm. Both kinds of vascular 

 fibres seem to follow the same path till they penetrate into the 

 kidney. 



It is still doubtful whether the spinal fibres from one side 

 innervate only the vessels of the kidney on the same side, or 

 partly those on the opposite side as well. It is also doubtful 

 whether the vagus contains fibres to the kidney. Certain experi- 

 ments carried out in Belgium by Masius (1888), in France by 

 Arthaud and Butte (1890), and repeated in Italy by Vanni 

 (1893), seemed to show that the vagi may exert a direct vasornotor 

 action on the kidneys, i.e. independent of the action of these 

 nerves on the heart and on arterial pressure. But this interpreta- 

 tion is excluded by the subsequent work of Walraweus (1896) 

 in Albertoni's laboratory. He shows : 



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