THE SYMPATHETIC SYSTEM. 503 



erally are ruddy in color, and the marginal veins are increased in size ; 

 while many venous branches, which were before imperceptible, become 

 distinctly apparent. The artery no longer exhibits its periodical con- 

 strictions, but remains in a state of permanent diastole, and the quantity 

 of blood circulating in the ear is consequently increased. 



A variety of secondary consequences follow from this condition. 

 First, the temperature of the ear is increased. A larger quantity of 

 blood from the interior of the body, passing through the vessels, com- 

 municates its warmth to the tissues of the part, and the elevation of 

 temperature is perceptible both by the touch and the thermometer. 

 Secondly, the blood in the veins becomes brighter, since in its more 

 rapid passage through the capillaries it loses less oxygen, and con- 

 sequently retains more nearly the hue of arterial blood. Thirdly, the 

 sensibility of the parts is increased and reflex actions from irritation of 

 the integument are more strongly pronounced. 



These results are not confined to the ear, but extend to all parts of 

 the head and face on the side of the section. The skin, the conjunctiva, 

 the mucous membranes of the mouth and nasal passages, even the 

 meninges of the brain, and, according to Vulpian, the fundus of the 

 eye when examined by the ophthalmoscope, all show an increased 

 vasculafity and more abundant circulation. 



The phenomena above described are increased in intensity by extir- 

 pation of the superior cervical ganglion of the sympathetic. They are 

 due to paralysis of the muscular coat of the arteries in the regions sup- 

 plied by sympathetic filaments from this source. Owing to this paral- 

 ysis, the arteries no longer offer their usual resistance to the pressure 

 of blood from the heart. Their relaxation admits a larger quantity to 

 the capillaries of the corresponding regions, and thus causes an in- 

 creased local circulation. 



These effects of division of the sympathetic are all reversed by its 

 stimulation. If the upper extremity of the divided nerve be subjected 

 to faradization, the arteries of the affected ear diminish in size, the 

 vascular congestion disappears, and the local temperature becomes 

 reduced to its normal standard, or even lower. The varying condition 

 of the blood-vessels under nervous influence is shown by an experiment 

 of Bernard,* in which the upper part of a rabbit's ear is cut off by 

 a clean incision, allowing the blood to escape in jets from the divided 

 arteries. The force and height of the jets having been observed, the 

 sympathetic nerve is divided in the neck on the corresponding side. 

 The blood at once escapes from the wounded ear in greater abundance, 

 and the arterial jets rise to double or triple their former height. The 

 galvanic current is then applied to the nerve, above the point of 

 section, when the streams of blood escaping from the wound diminish 

 or disappear ; but they recommence when the galvanization of the nerve 

 is suspended. 



* Journal de la Physiologic. Paris, 1862, p. 397. 



