THE VASODILATOR CENTER AND NERVES. 771 



reflex irritation. On the other hand, the clinical picture has been explained by 

 assuming that the exophthalmos and the goiter are results of paralysis of the 

 vasomotors, which gives rise to distention of the vessels. The increased action 

 of the heart is looked upon as a sign of diminished or abolished action of the cardiac 

 inhibitory fibers of the vagi. All of these phenomena, it is said, can be induced by 

 injury of the upper portion of the restiform body on each side in rabbits, and 

 according to Durdufi below the auditory tubercle. 



Landois was the first, in 1866, to describe and designate as vasomotor angina 

 pectoris an affection of paroxysmal occurrence involving either all or at least 

 a large number of the vasomotor nerves. In consequence of intense irritation 

 the vessels undergo contraction; the arteries are hard and small, the skin, espe- 

 cially of the hands and the feet, pallid and cold, and at the same time the seat 

 of formication and prickling at the tips of the fingers. The increase in blood- 

 pressure brought about by the vascular contraction causes enormous acceleration 

 of pulse, together with a feeling of oppression, of vertigo, of fear, of abolition of 

 the vital functions and even painful palpitation of the heart. 



The appearance of sudden hyperemia, with transudation and ecchymoses in 

 individual thoracic or abdominal viscera must likewise be referred to an angio- 

 neurotic origin. In this connection it should be recalled that Schiff, Brown- 

 S6quard and others observed hyperemia and extravasations of blood in the lungs, 

 the pleurae, the intestines and the kidneys, after injury of the pons, the striate 

 body and the optic thalamus. Crushing or section of one-half of the pons causes, 

 according to Brown-Sequard, especially extravasations of blood into the lung of 

 the opposed side. The same observer noted also extravasations of blood into 

 the capsules of the kidneys after injury to the lumbar cord. The pulmonary vessels 

 may be relaxed through the intermediation of the nerves, and attacks of asthma 

 may thus be induced. Rarely, the vasomotor distribution upon an entire side of 

 the body has been observed to be irritated or paretic. 



The dependence of glycosuria upon vasomotor influences has been pointed out 

 on p. 313, the influence of the vasomotors upon the urinary secretion on p. 514. 

 The effect of fever upon the vasomotor nerves in the form of irritation is shown 

 by the pale skin in the stage of chill attending some fevers, followed by redness 

 in consequence of consecutive paralysis. Sudden elevation of temperature of 

 paroxysmal occurrence has been considered as a sign of irritation of the vasomotor 

 center in the medulla. 



Little is known concerning affections in the distribution in the veins dependent 

 upon the nerves. Moltschanoff observed that in the sequence of inflammation 

 of the ulnar and median nerves, with anesthesia, venous dilatation occurred in 

 the distribution of the basilic vein. 



It should, finally, be pointed out that sensory nerves in the form of delicate 

 networks have been found on the blood-vessels. Pathological manifestations of 

 pain in the course of the vessels, in association with arterial spasm, aneurysm, 

 arteriosclerosis, and thrombosis, are probably indicative of morbid states of irrita- 

 tion of the nerves. 



THE VASODILATOR CENTER AND NERVES. 



Although a center for vasodilator or vessel-relaxing nerves has not 

 yet been demonstrated, the existence of such a center in the medulla 

 may nevertheless be suspected. It would, thus, be the antagonist of the 

 vasomotor center. The center is, in any event, not in a state of per- 

 manent (tonic) irritation. The vasodilator nerves are analogous in 

 function to the cardiac branches of the vagus, as irritation of both causes 

 relaxation in the state of rest. The nerves may, therefore, be designated 

 vaso inhibitory nerves. A dyspneic state of the blood irritates the center 

 (as it does also that for the vasomotors), and, as a result, especially the 

 cutaneous vessels are dilated, while at the same time the vessels of the 

 internal organs become anemic in consequence of simultaneous irri- 

 tation of the vasoconstrictors. Chloral hydrate in small doses is a stimu- 

 lant to the vasodilators. Irritation of the depressor nerve also excites 

 them reflexlv. 



