CIRCULATION. 483 



literature, but it was not until Henle demonstrated the existence of muscular 

 elements in the middle coats of the arteries in 1840 that a secure foundation 

 was laid for the present knowledge of the mechanism by which that contractility 

 is made to control the distribution of the blood. More than a hundred years 

 before, indeed, Pourfour du Petit had shown that redness of the conjunctiva 

 was one of the consequences of the section of the cervical sympathetic, but had 

 called the process an inflammation, in which false idea he was supported by 

 Cruikshank and others ; and Dupuy of Alfort had noted redness of the con- 

 junctiva, increased warmth of the forehead, and sweat-drops on ears, forehead, 

 and neck following his extirpation of the superior cervical ganglia in the 

 horse ; Brachet, also, cutting the cervical sympathetic in the dog, had gone so 

 far as to attribute the resulting congestion to a paralysis of the blood-vessels. 

 But these were merely clever speculations, for the anatomical basis necessary 

 for a real knowledge of this subject was wanting as yet. Henle furnished this 

 basis, and at the same time reached the modern point of view. " The part 

 taken by the contractility of the heart and the blood-vessels in the circulation," 

 said Henle, " can be expressed in two words : the movement of the blood depends 

 on the heart, but its distribution depends on the vessels." Nor did Henle stop 

 here. It was now known that the vessels possessed contractile walls ; it was 

 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 Schiif, Bernard, Brown-Sequard, and Waller, 1 

 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 2 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 3 announced that "if galvanism is applied 



1 Waller, 1853, p. 378. The literature of vaso-motor nerves is so large that only works of 

 the past fifteen years can be cited, except in a few important instances. 



4 Bernard, 1851, p. 163. Brown-Sequard, 1852, p. 490. 



