208 BIOLOGY. [Book ii. 



centre of these movements, as well as of almost the totality of 

 the vaso-motory nervous network, seems to be situated in the up- 

 per part of the spinal marrow. According to experiments of M. 

 Schiffi the section of the cervical marrow abolishes in the rabbit 

 the rhythmical movements of which we have spoken. The com- 

 plete section abolishes them on the two sides ; the hemisection 

 abolishes them only on the seotionised side.' 



If we can paralyse the vessels, especially the arteries, by sec- 

 tionising the nerves which ardmate them, or the excitatory centre 

 of those nerves, we can inversely excite arterial contractions by 

 diverse means. The mere action of cold suffices to determine 

 the contraction even of large arteries. Thus we can in a sheep 

 stop the hsemorrhage produced by the section of the carotid 

 artery by applying to this section a simple sponge saturated 

 with cold water. ^ In an amputated limb, Kblliker det;rmined 

 the contraction of the poplitic artery, and of the tibial artery, by 

 help of a magneto-electrical apparatus of induction.^ This is an 

 effect which we obtain in all the arteries by electrising them with 

 interrupted currents. • M. Vulpian has observed the contraction 

 effected slowly at the outset between the two electrodes applied 

 to the vessel, then propagated to the last peripheric ramifications, 

 The continuous electric currents, whatever their direction might 

 be, would act in an analogoiis manner.* 



The arteries, like the heart, never rest during life. Their 

 action appears even to survive that of the heart, which thus no 

 longer deserves to be called ultimum. moriens, a nam.e long given to 

 it. When the heart has ceased to beat the arteries still contract, 

 and'as their action is no longer counterbalanced by the cardiacal 

 impulse, they tend to drive the blood into the capillaries and into 

 the veins. Then when their muscular coat is dead in its turn, they 



' Schiff, Sur un Oceur Artificiel Accessoire dans Us Lapins {Comptes Eendus 

 e. I'Acad. des Sc, t. XXXIX. 1834). 



2 Vulpian, Zefons sur VAppareil Vaso-moteur, p. 63. 



3 Kblliker, Zeitschrift filr WisseTisoh. Zoologie, 1849. 

 * Vulpian, loe. cit., p. 56, 



