1889.] The Innervation of the Renal Blood-vessels. 363 



The principal conclusions arrived at in this communication will be 

 arranged under the following three headings : 



I. The Origin and Course of the Vaso-constrictor Nerves. 



II. The Origin and Course of the Vaso-dilator Nerves. 



III. The Reflex Phenomena of the Renal Vessels. 



It will be necessary, however, to describe shortly the method em- 

 ployed. The general blood pressure and the volume of the kidney as 

 measured by Boy's oncometer were recorded simultaneously, together 

 with a time tracing and a lever marking the moment and duration of 

 the nerve excitation. In this manner both the general and the local 

 effects of any given stimulation were determined simultaneously. The 

 method of preparation of the nerves was as follows : the roots of the 

 nerves were exposed inside the spinal canal, the posterior roots were 

 then divided inside the dura mater, and the entire nerve outside the 

 dura mater arranged for stimulation with suitable electrodes. In 

 some cases the nerves were cut and ligatured and the distal ends 

 excited. By the use of one or other of these methods, the danger of 

 the exciting current spreading to the cord, and so producing reflex 

 effects, was reduced to a minimum. In many experiments this 

 danger was further eliminated by dividing the cord above the level of 

 the nerves excited. 



In this communication a nomenclature is adopted which assumes 

 that the dog has twenty dorso-lumbar vertebrae, of which thirteen 

 are dorsal and seven lumbar. For excitation an ordinary Du Boia 

 coil was used with Helmholtz's modification, and the rate of interrup- 

 tion was varied, as will be mentioned more fully below from fifty per 

 second to one per second. 



The anaesthetics used were chloroform and morphia, and after the 

 completion of the necessary operative procedure, the animals were 

 curarised, artificial respiration and anassthetisation being maintained 

 in the usual manner. 



It is well known that, when either the renal nerves or the splanch- 

 nic nerves are excited, a contraction of the kidney accompanied by a 

 rise of blood pressure is observed. On exciting the lower dorsal 

 nerves inside the spinal canal the same general facts are observed, 

 provided the posterior roots have been divided and care be taken to 

 prevent the spreading of the exciting current to the cord. Before 

 entering into further detail it is necessary to state that in order to get 

 these effects the rate of excitation must not be slower than five per 

 second. Hence, unless otherwise mentioned, it is to be understood 

 that the rate of stimulation was a rapid one, i.e., fifty per second. 



I. Origin and Course of the Vaso-constrictor Nerves. 



No effects have been observed to follow the excitation of the peri- 

 pheral end of a divided posterior root. Furthermore, the same 

 VOL. XLV. 2 B 



