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



result is seen to follow the stimulation of the divided anterior root, 

 and the stimulation of the entire nerve outside the dura mater after 

 previous section of the posterior root. Hence we may conclude that 

 no efferent vasomotor fibres are contained in the posterior roots. 



Excitation of the anterior roots, or of the entire nerve after pre- 

 vious division of the posterior root, is followed by contraction of the 

 kidney and rise of general blood pressure when any nerve from the 

 6th dorsal to the 2nd lumbar is placed on the electrodes. Excitation 

 of the higher nerves, e.g., the 4th or 5th dorsal, produces but slight 

 effects on the general blood pressure, and in the higher ones still, i.e., 

 the 2nd or 3rd, the accelerator fibres are met with in abundance, and 

 hence a small rise of pressure (due to this cardiac effect) is produced. 

 On the other hand, the 3rd lumbar has in many cases yielded no re- 

 sult on excitation, but occasionally a slight rise of general blood 

 pressure has been observed. So that the 6th dorsal and the 2nd 

 lumbar are practically the limits of the series of nerves, the stimula- 

 tion of which causes any marked effects either on the kidney or on the 

 general arterial tension. 



The effects, however, are not equally marked with all these nerves. 

 The lower dorsal nerves, i.e., from the 10th to the 13th, produce much 

 greater effects, both on the kidney and on the general blood pressure, 

 than either the nerves above them or those immediately below them. 

 So that although all the nerves from the 6th dorsal to the 2nd 

 lumbar may contain fibres for the renal vessels, still their main 

 supply is derived from the 10th, llth, 12th, and 13th dorsal nerves. 



It follows from the above description that there is no very great 

 separation between the paths followed by the nerves for the kidney 

 vessels and those destined for the vessels of the other abdominal vis- 

 cera. However, the lower dorsal not only produce greater effects on 

 the kidney and on the general blood pressure than the upper dorsal 

 nerves, but what is more important the two effects do not vary directly 

 with one another. Although usually a nerve producing a large renaJ 

 contraction causes simultaneously a great rise of pressure, yet this is 

 by no means invariably the case, and a small renal contraction may 

 be accompanied by a great rise of pressure and vice versa. The 12th 

 and 13th dorsal nerves, for instance, cause usually a great renal con- 

 traction, but the accompanying rise of blood pressure is not so high 

 s with some of the nerves above them. Hence we must conclude 

 that in individual cases there may be small variations in the number 

 of fibres going on the one hand to the kidney and on the other hand 

 to the other abdominal viscera. 



The contraction of the kidney occurs after a short latent period, 

 and in a typical case it is sudden, marked, and very persistent, often 

 lasting long after the excitation has ceased. The kidney then com- 

 mences slowly to expand and along with this expansion the blood 



