4:36 NERVOUS SYSTEM. 



show that the vaso-motor nerves are derived exclusively from 

 the cerebro-spinal system, and do not originate in the sym- 

 pathetic ganglia. "Without citing the numerous confirmatory 

 observations of different physiologists, it is sufficient to state 

 that Schiff has experimentally demonstrated, in the most 

 conclusive manner, that the vaso-motor nerves are derived 

 from the cerebro-spinal centres and not from the sympathetic 

 ganglia. 1 There is now no difference of opinion among physi- 

 ologists upon this point, the only question being the exact 

 location of the vaso-motor centres. Ludwig and Thiry found 

 that section of the cord in the upper cervical region produced 

 dilatation of most of the blood-vessels of the organism, but 

 notably of the mesenteric vessels, and that galvanization of 

 the cord at its lower cut extremity caused the vessels to con- 

 tract. 2 These observations have been repeatedly confirmed. 

 As a summary of our present knowledge of the origin 

 of the vaso-motor nerves in the cerebro-spinal axis, we may 

 cite the following remarks, from a review of the experiments 

 of Schiff, by Brown-Sequard : " 1. That if there are vaso- 

 motor elements which decussate in the spinal cord, their 

 number is excessively small. 2. That the facts observed 

 by M. Schiff, on this subject, admit of a more simple ex- 

 planation. 3. That a number of the vaso-motor elements 

 stop in the spinal cord. 4. That a tolerably large number 

 of vaso-motor elements, coming from different points in the 

 body, ascend as far as the tuber annulare, and some as far as 

 the cerebellum and to other parts of the encephalon. 5. 

 That consequently, the medulla oblongata is not the sole 

 source of the vaso-motor elements." 5 These statements 

 express pretty much all that we know of the origin of the 

 vaso-motor elements and their decussation, as far as their 



1 SCHIFF, JTntersuchungen zur Physiologic des Nerveiisystems, Frankfurt am 

 Main, 1855, S. 167, et seq. 



2 LUDWIG UNO THIRY, Uber den Einfiuss dcs Halsmarkes a>if den Blntstrom. 

 Sitzungs-berichte der mathematischnaturwissemchaftliclien Classe dcr kaiserlichen 

 tlkademie der Wissenschaften, Wien, Bd. xlix., ii Abtheilung, S. 421, et scq. 



3 Journal de la physiologie , Paris, 1858, tome i., p. 214. 



