366 Dr. J. R. Bradford. [Feb. 21, 



not by any expansion, but by a passive contraction of the kidney 

 vessels. In other words, with these higher nerves a dilatation is 

 produced, not only of the kidney vessels, but also of the vessels of a 

 much larger area, and hence the renal dilatation is unable to mani- 

 fest itself. 



This view is confirmed by the results obtained on excitation of the 

 splanchnic nerve. When this nerve is stimulated with quick rates, 

 the kidney, as is well known, undergoes great contraction, and there 

 is at the same time a large rise in the general blood pressure. With 

 slow rhythmical stimulation, however, I have never succeeded in 

 getting any renal expansion. This slow stimulation, however, causes 

 a large fall in the blood pressure, accompanied by a marked renal 

 contraction. This renal contraction is obviously passive, since it not 

 only exactly follows the fall of blood pressure, but, when the exciting 

 current is shut off, the blood pressure undergoes a sudden and tem- 

 porary rise, and this rise is accompanied by a correspondingly transi- 

 tory renal expansion. In other words, the dilatation is one produced 

 in a large area, and the kidney vessels are affected secondarily. 

 Hence just as the renal constrictor fibres are best marked in the llth, 

 12th, and 13th dorsal nerves, so the same is true for the dilator. 

 These, however, like the constrictors, probably exist in the higher 

 nerves, but for the reasons given it is almost impossible to demon- 

 strate their existence positively, as they run with the dilator fibres 

 for the vessels of the other abdominal viscera. 



Excitation of the peripheral end of the divided vagus in the neck 

 causes of course marked contraction of the kidney, owing to its inhi- 

 bitory action on the heart, which action is not obviated by the doses 

 of curare employed. After small doses of atropine the stimulation of 

 the cervical vagus has no effect on the volume of the kidney. Stimu- 

 lation of the vagus in the thorax, i.e., beyond the point where it gives 

 off its cardiac fibres, has also no effect on the volume of the kidney. 

 Thus we may conclude that there is no evidence to show that the 

 vagus supplies any fibres to the renal vessels. 



III. The Reflex Phenomena of the Renal Vessels. 



Excitation of the central end of the divided sciatic causes, as shown 

 by Boy, a contraction of the kidney accompanied by a rise of blood 

 pressure. This result I can confirm, as it occurs in by far the greater 

 number of cases. Occasionally, however, this nerve causes a slight 

 expansion of the kidney, but this is not only very small in amount, 

 but it is also very rare. Sometimes, as is well known, the central 

 end of the sciatic causes a fall of blood pressure, and when this occurs 

 it is accompanied by a renal contraction. The central end of a 

 divided intercostal nerve causes a slight rise of blood pressure, accom- 

 panied by a small contraction of the kidney vessels. 



