342 PHYSIOLOGY CHAP. 



division of the cervical sympathetic, after which the notion of 

 vascular nerves became familiar. 01. Bernard was more struck 

 by the marked rise of temperature in all parts supplied by the 

 sympathetic than by the dilatation of the vessels, so much so 

 that in 1852 he gave an erroneous interpretation of the same, 

 declaring the sympathetic to be a thermal nerve. Shortly after- 

 wards, however, Brown - Sequard completed the discovery by 

 describing the converse phenomena that occur in the vessels of 

 the ear, when the peripheral end of the divided nerve is excited 

 by an electrical stimulus. This he rightly interpreted as meaning 

 that the primary effects were dilatation and constriction of the 

 vessels, the secondary effects, the warming or cooling of the parts 

 supplied ; and he gave the name of vaso-constrictors to the rami 

 auriculares of the cervical sympathetic system. A. Waller almost 

 simultaneously confirmed these same facts and their significance, 

 without knowing of Brown-Se'quard's publication. 



In 1854, M. Schiff, observing the vessels of the rabbit's ear by 

 transmitted light, described an irregular succession of contractions 

 and dilatations, which are much slower than the rhythm of the 

 heart, and quite independent of it. Owing to these undulations, 

 the flow of blood through the ear alternately diminishes and 

 increases (ischaemia and hyperaemia), with a consequent fall and 

 rise of its temperature, blood pressure, and volume. 



In 1856 he showed indirectly that besides the vaso-constrictors, 

 vaso-dilators are also present in the cervical sympathetic, so that 

 the rhythm, which he detected in the vessels of the ear, must be 

 regarded as the result of the alternate functional predominance 

 of one or other kind of vasomotor nerve. He found when the 

 animal was artificially warmed some days after dividing the 

 cervical sympathetic, or was forced to take violent movements, or 

 infected with a septic or toxic fever, that the vessels of the ear 

 on the normal side showed much greater vascular dilatation, 

 hyperaemia and heating than those on the operated side, a fact 

 which led Schiff to the conclusion that the former were under 

 the control of dilator nerves, which in the second case had been 

 divided. 



Schiff s view was brilliantly confirmed in 1858 by Claude 

 Bernard, who discovered the effect produced in the vessels of the 

 subm axillary gland of the dog, by electrical stimulation of that 

 branch of the facial nerve which traverses the tympanic cavity, 

 joins the lingual branch of the trigeminal, and then under the 

 name of chorda tympani passes partly into the tongue, partly to 

 the submaxillary and sublingual glands. That the chorda 

 tympani contains vaso-dilator fibres is shown by the fact that its 

 stimulation produces marked hyperaemia of all the vessels of the 

 submaxillary gland, associated with such marked acceleration of 

 the blood-stream that the flow through the glands has scarcely 



