CIRCULATION. 193 



known further that these walls contracted when mechanically stimulated; for 

 example, by scraping them with the point of a scalpel ; and various observers 

 had traced sympathetic nerves from the greater vessels to the lesser until lost in 

 their finest ramifications. It was therefore easy to construct a reasonable 

 hypothesis of the control of the blood-vessels by the nerves. Henle declared 

 that the vessels contract because their nerves are stimulated, either directly, 

 or reflexly through the agency of a sensory apparatus. The ground was 

 thus prepared for the physiological demonstration of the existence of " vaso- 

 motor" nerves, as Stilling began to call them. Four names are associated 

 with this great achievement — Schiff, Bernard, Brown-Sequard, and Waller, 

 each of whom worked independently of the others. Foremost among them 

 is Claude Bernard, though not the first in point of time, for it was he who 

 put the new doctrine on a firm basis. In his first publication Bernard stated 

 that section of the cervical sympathetic, or removal of the superior cervical 

 ganglion, in the rabbit, causes a more active circulation on the correspond- 

 ing side of the face together with an increase in its temperature. The greater 

 blood-supply manifests itself in the increased redness of the skin, particularly 

 noticeable in the skin of the ear. The elevation of temperature may be easily 

 felt by the hand. A thermometer placed in the nostril or in the ear of the 

 operated side shows a rise of from 4° to 6° C The elevation of temperature 

 may persist for several months. Similar results are obtained in the horse and 

 the dog. 



The following year Brown-Sequard announced that " if galvanism is applied 

 to the superior portion of the sympathetic after it has been cut in the neck, the 

 dilated vessels of the face and of the ear after a certain time begin to contract ; 

 their contraction increases slowly, but at last it is evident that they resume 

 their normal condition, if they are not even smaller. Then the temperature 

 diminishes in the face and the ear, and becomes in the palsied side the same as 

 in the sound side. When the galvanic current ceases to act, the vessels begin 

 to dilate again, and all the phenomena discovered by Dr. Bernard reappear." 

 Brown-Sequard concludes that "the only direct effect of the section of the 

 cervical part of the sympathetic is the paralysis, and consequently the dilata- 

 tion, of the blood-vessels. Another evident conclusion is that the cervical 

 sympathetic sends motor fibres to many of the blood-vessels of the head." 



While Brown-Sequard was making these important investigations in 

 America, Bernard, in Paris, quite unaware of Brown-Kequard's labors, was 

 reaching the same result. The existence of nerve-fibres the stimulation of 

 which causes constriction of the blood-vessels to which they are distributed was 

 thus established. 



A considerable addition to this knowledge was presently made by Schiff, 

 who pointed out in 185b' that certain vaso-motor nerves take origin from the 

 spinal cord. The destruction of certain parts of the spinal cord causes the 

 same vascular dilatation and rise of temperature that follows the section of the 

 vaso-motor nerves outside the spinal cord. 



At this time Schiff also offered evidence of vaso-dilator nerves. When 

 Vol. I.— 13 



