326 OF THE CIRCULATION OF THE BLOOD. 



exceeding the normal ; this is the result of the moderate application of cold, 

 and of mechanical and galvanic irritation. (3.) Constriction either does not 

 take place at all, or when it does, it very rapidly gives place to great dilata- 

 tion ; this is the effect of a weak solution of sulphate of copper, of a strong 

 solution of common salt, of wine, of opium, and of spirit of wine. (4.) Dilata- 

 tion, preceded or not by momentary constriction, may slowly yield to con- 

 striction, which remains permanent ; this is the effect of sulphate of copper, 

 applied in strong solution, or in substance. The electric stimulus is most 

 effectual when applied by the magneto-galvanic apparatus. When the mi- 

 nute arteries of the mesentery of frogs, between yth and y'^th of a Paris line in 

 diameter, are thus stimulated, they do not immediately respond to the irrita- 

 tion, but begin to contract after a few seconds, so that their diameter, in from 

 five to ten seconds, is diminished by a third, and their sectional area conse- 

 quently reduced to about half; by a continued application of the stimulus, 

 the calibre is so much reduced, that only a single row of corpuscles can pass ; 

 and at last the vessels become completely closed, and the current of blood 

 arrested, the original conditions being gradually restored on the cessation of 

 the electric current (Weber). 1 Further, it has been ascertained by the ex- 

 periments of Poiseuille (which confirm those of John Hunter), that when an 

 artery is dilated by fluid injected into it, it reacts with a force superior to the 

 distending impulse; and that, if a portion of an artery from an animal re- 

 cently dead (in which the contractility is preserved), and one from an animal 

 that has been dead some days (in which nothing but the elasticity remains), 

 be distended with an equal force, the former becomes much more contracted 

 than the latter, after the distending force is removed. 



253. There is no sufficient proof that the contractility of the arteries en- 

 ables them to exert a propulsive action in any marked degree supplementary 

 to that of the Heart ; and yet, looking to the general facts already stated, 

 as to the diffusion of the propulsive power through the arterial trunks in 

 many of the lower animals, their experimentally proved reaction upon a 

 distending force, and to the circumstance, that a kind of rhythmical action, 

 occurring seven or eight times in the minute, has been observed by Wharton 

 Jones in the vessels of the Bat, by Schiff in those of the ear of the Rabbit, 

 by Loveu 2 and RiegeP in the sapheuous artery of the Rabbit, which last con- 

 tracts once or twice in the minute, and by Saviotti 4 and Gunning 5 in the vessels 

 of the web of the foot in the Frog, it does not seem by any means improbable 

 that some such power should be preserved, even where there is the greatest 

 concentration of the propulsive force in the muscular walls of the Heart. It 

 is important to notice that these systolic and diastolic movements of the vessels 

 are not simultaneous on opposite sides of the body, and that they are quite 

 independent of cerebro-spinal iuuervation, since they continue even when the 

 whole of the cerebro-spinal and sympathetic nerves have been divided, and 

 even after division of the spinal cord itself in the neck. 6 



254. The influence of the Nervous system upon the calibre of the vessels, 

 which might be inferred to exist from the act of blushing and other analogous 

 phenomena, is capable of experimental demonstration. Thus evidence has 

 been afforded by the experiments of Dr. Aug. Waller 7 that the application 

 of galvanism to the sympathetic trunk on either side of the neck causes cou- 



1 M oiler's Arclnv, 1847. 2 Loven, Liulwi^'s Arbeiten, 1860, p. 1. 



3 Kie^el, I'lln-er's Archiv, 1871. 4 Saviotti, Virchmv's Archiv, lid. 1, 1870. 



6 (iuniiiii^, Onderzoeckingen, etc-., Utrecht, 18- r >7. 



6 Sec Krunton, in Ludwig's Arbeiten, lid. iv, 1870, p. 106. 



7 Sec Cnmpies Kendus, 1853, torn, xxxvi, p. 378. Of this remarkable experiment, 

 which first demonstrated the influence of the Sympathetic Nerve upon the smaller 

 arteries, the Author, by the kindness of Dr. Waller, has himself been a witness. 



