694 VASO-MOTOR NERVES OF KIDNEY. [BOOK n. 



spoken of as the vaso-constrictor region of the spinal cord. They 

 issue from the spinal cord by the anterior roots of a large number 

 of the spinal nerves taking origin from this region, and may be 

 traced (in the dog) as high up as the 6th thoracic, a few perhaps 

 even to the 4th thoracic, and as low down as the 4th lumbar, 

 corresponding to the 2nd lumbar in man; but most seem to 

 pass by the llth, 12th and 13th thoracic nerves. Passing through 

 the corresponding ganglia of the sympathetic chain, these fibres 

 reach the solar plexus and thus the renal plexus by the splanchnic 

 nerves ; those however coming from some of the lower nerves 

 apparently do not contribute to the splanchnic nerves, but take 

 a separate course. Centrifugal stimulation of these anterior 

 roots produces shrinking of the kidney, all the more marked and 

 distinct in the case of the llth, 12th and 13th dorsal roots 

 because the effect on the kidney is then not so much masked 

 by vaso-motor effects on other organs. Stimulation of the higher 

 roots also produces shrinking of the kidney but less marked, since 

 in these cases the stimulation bears at the same time largely on 

 vaso-constrictor fibres for other abdominal organs, and so by raising 

 the general blood-pressure tends to neutralize the local effect on 

 the kidney. And even the very decided shrinking of the kidney 

 which results from the stimulation of the splanchnic trunk itself 

 is less than would take place if the stimulation affected the vessels 

 of the kidney only. 



413. We stated in 168 that by the method of slowly 

 repeated rhythmical stimulation the presence of vaso-dilator fibres 

 in the sciatic nerve might be detected, though these are largely 

 mixed with vaso-constrictor fibres ; and slow rhythmical stimu- 

 lation of the anterior roots of the above-mentioned lower thoracic 

 nerves leads, not, as does ordinary rapidly interrupted stimulation, 

 to shrinking, but to swelling of the kidney, shewing that these 

 roots contain vaso-dilator fibres as well as vaso-constrictor fibres. 

 The higher (anterior) roots also appear to contain some renal 

 vaso-dilator fibres ; but the effect of stimulating them by the 

 slow rhythmic method is more masked by a concomitant dilation 

 of the vessels of the other abdominal organs, the roots in 

 question containing vaso-dilator as well as vaso-constrictor fibres 

 for those organs ; this leads to a fall of general blood-pressure 

 whereby the tendency of the kidney to swell is counteracted. As 

 far as can be ascertained at present the paths of the renal vaso- 

 dilator fibres are similar to those of the renal vaso-constrictor 

 fibres. 



The kidney then is well supplied, especially through the 

 anterior roots of the lower thoracic nerves, with vaso-constrictor 

 fibres, and is also supplied with vaso-dilator fibres. Some results 

 have seemed to shew that the fibres passing along the roots 

 of one side of the spinal cord govern the vessels not only of 

 the kidney of the same side but also to a certain extent of the 



