454 BIOLOGY. [Book vii. 



the section of a nervous sympathetic cord, the venous blood 

 coming from the organs whose circulation was controlled by this 

 nervous branch becomes redder, warmer, and more coagulable. 

 It is less bm-ned, and contains more oxygen, but it has been 

 the seat of active chemical reactions, for it contains less fibrine 

 than ordinary venous blood ; besides, it springs from the vein 

 in isochronal jerks, corresponding to the pulsations of the 

 heart. 



This is because the capillaries are dilated, and allow the san- 

 guineous current to pass with five or six times more than its 

 ordinary rapidity. Generally, there is in the organ whose vaso- 

 motors are paralysed a sanguineous congestion, and always an 

 elevation of the local temperature. Let the sectionised nerve be 

 electrised, and immediately the capillaries contract, congestion 

 disappears, the local temperature falls, the venous blood becomes 

 again black, and no longer flows except foamingly.^ 



Since by paralysing the vaso-motory branches the elevation of 

 the local temperatures is provoked, we are authorised in conclud- 

 ing therefrom that the nervous network of the large sympathetic 

 performs the function of moderating local combustions, of re- 

 straining the nutritive expenditure, of rationing the anatomical 

 elements, of creating coldness.^ 



But we have seen that the sympathetic nervous network is 

 only a dependency of the general nervous system, that it is 

 anatomically connected with the nervous centres, and that there 

 is, in the upper part of the spinal marrow, a general vaso-motory 

 centre. It will, then, be easy to comprehend that excitations, 

 direct or reflex, but having their seat in the nervous centres, can 

 make all, or nearly all, the capillary vessels of the body contract 

 synergetically ; and, in fact, by wounding or cutting the spinal 

 marrow at a particular point, we can provoke iu the mammifers, 

 for example rabbits and guinea-pigs, a general coldness,' which 

 throws these animals into a state resembling hibernal sleep. The 



1 CI. Bernard, JRevm Scientifique, 1872, Ho. 23. ^ Ibid. 



8 01. Bernard, Bapport sur Us ProgrU de la Physidlogie, p. 183. 



