CHAP. XXIII. ] 



OF THE HUMAN BRAIN. 



475 



proceed from or to the Viscera are mostly distributed along 



the course of the Blood-vessels. Some of the fibres 



of this system are specially distributed to the coats 



of the Vessels, and are, from the nature of their 



functions, known as 'vaso- 



motor nerves.' A portion of 



these must have ' afferent ' func- 



tions whilst others transmit 



' efferent ' impulses, causing the 



vessels to contract, so that by 



means of such nerves, the 



amount of blood flowing through 



particular vascular territories 



may be easily regulated. The 



' vaso-motor ' nerves are con- 



nected with small ganglia dis- 



tributed over the vessels. To 



some extent motor stimuli 



emanate from these, though the 



whole ' Vaso-motor ' system of 



the body seems to be amenable 



to the influence of a 'regulative 



centre ' situated in the Medulla, 



together with other subordinate 



Centres in the Spinal Cord. 



Whilst the Sympathetic Sys- 



FIG. 170. One of the Sympathetic 

 Ganglia from the right Lateral Cord 



probably Contains its OWn thetic ; Re, Re, two communicating 

 , . . branches ; Spl, Splanchnic or Vis- 



mtrmsic afferent and efferent cera i ner ve ; , small nerve ; G, g an- 

 nerves, it also seems to send g Uon cells and fibres - < x about * 



diameters.) 



(through the before-mentioned 



communicating filaments) afferent nerves to the grey 

 matter of the Spinal Cord, and to receive therefrom certain 

 efferent motor and other fibres. This great Sympathetic 

 System of nerves is to a certain extent an independently 



