CHAP. XXI.] FUNCTIONS OF THE SYMPATHETIC. 1 45 



that the peristaltic movements of the intestines will continue under 

 similar circumstances. 



This peculiarity seems to be referable to a double cause ; first, 

 the disposition of the muscular fibres themselves, which is such that 

 a contraction cannot take place at one part without affecting the 

 adjacent fibres, so that the contraction of one set of fibres appears 

 to stimulate those in their immediate vicinity. This progressive 

 contraction is well seen in the intestines. Secondly, the frequent 

 occurrence of small ganglia, not only among the plexuses of the 

 sympathetic, but also, as in the heart, upon or among the muscular 

 fibres themselves. These ganglia, it is reasonable to suppose, are 

 so many little magazines of nervous force, which, by their intimate 

 connexion with the muscular fibres themselves, render them capa- 

 ble of repeating their action at intervals, after their disconnexion 

 from the main trunk of the sympathetic system. 



Much, however, in the peristaltic actions, is perhaps due to the 

 peculiar constitution of the unstriped muscular fibre itself; a con- 

 stitution which gives it a slow and enduring, rather than a quick, 

 energetic, and fleeting contraction. The actions of the heart are 

 intermediate to those of the intestine and of voluntary muscle, and 

 so are its muscular fibres, which, while they exhibit the striped 

 appearance of voluntary muscle, are nevertheless devoid of the sar- 

 colemma, and interlace in a peculiar manner with each other. The 

 gelatinous nerve -fibres exhibit the same apparent inferiority of 

 organization as the unstriped muscular fibre. It is a remarkable 

 confirmation of these views, that in the tench (Cyprinus tinea), 

 according to Ed. Weber, in which the muscular fibres of the ali- 

 mentary canal are of the striped kind, there is no peristaltic action 

 of the intestines, and that the application of a rapid succession of 

 electrical shocks from a magneto-electric rotation instrument, causes 

 that sudden and quick contraction which characterises the striped 

 muscular fibre.* 



An observation made by Pourfour du Petit, f many years ago, 

 suggested an office of the sympathetic, distinct from sensation or 

 ordinary motion, but apparently not less important than either. 

 He found that the division of the trunk of the sympathetic in dogs, 



* By experiments with the magneto-electric instrument, E.Weber has given 

 additional illustration of the fact, that the peristaltic contraction is character- 

 istic of the unstriped fibre, and that the sudden and quick contraction is pe- 

 culiar to the striped fibre. See his elaborate article, " Muskelbeweguug," in 

 Wagner's Handworterbuch, 1846, and our remarks at pp. 185, 192, 193, vol. i. 



t Histoire de 1'Acad. Koyal des Sciences, an. 1727, etc. Lettres concernant 

 des reflexions sur les decouvertes faites sur les yeux, 1732. 



VOL. II. L 



