484 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



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-Se"quard 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-Se"quard was making these important investigations in 

 America, Bernard, in Paris, quite unaware of Brown-Se"quard'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, 1 

 who pointed out in 1856 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 

 the left cervical sympathetic is cut in a dog, and the animal is kept in his 

 kennel, the left ear will always be found to be 5 to 9 warmer than the 

 right. If the dog is now taken out for a run in the warm sunshine, and 

 allowed to heat himself until he begins to pant with outstretched tongue, the 

 temperature of both ears will be found to have increased. The right ear is 

 now, however, the warmer of the two, being from 1 to 5 warmer than the 

 left. The blood-vessels of the right ear are, moreover, now fuller than those 

 of the left. When the animal is quiet again the former condition returns, the 

 redness and warmth in the right becoming again less than in the left ear. The 

 increase of the redness and warmth of the right ear over the left, in which the 

 vaso-constrictor nerves were paralyzed, must be the result of a dilatation of 

 the vessels of the right ear by some nervous mechanism. For if the dilatation 

 of the vessels was merely passive, the vessels in the right ear could not dilate to 

 a greater degree than those in the left ear which had been left in a passive state 

 by the section of their nerves. This experiment, however, is by no means con- 

 clusive. 



The existence of vaso-dilator fibres was placed beyond doubt by the follow- 

 ing experiment of Bernard 2 on the chorda tympani nerve, new facts regarding 

 the vaso-constrictor nerves being also secured. Bernard exposed the submax- 

 illary gland of a digesting dog, removed the digastric muscle, isolated the 

 nerves going to the gland, introduced a tube into the duct, and, finally, sought 



1 Schiff, 1856, p. 69 ; 1859, p. 153. 



2 Bernard, 1858, p. 241 ; see also pp. 649 to 658. 



