EXTRACT VIII. c. 



ON THE CIRCULATION AND EXCRETION OF THE 

 CEREBRO-SPINAL FLUID. 



AGAIN the cerebro-spinal fluid, being that fluid which 

 surrounds and interpenetrates the whole systemic nervous 

 system, separating the layers of its encircling membranes 

 or mem'nges and neurilemmae, thereby preventing friction 

 and concussion amongst its component parts and floating 

 them, so to speak, within a fluid medium which, during 

 neuro-muscular activity, secures their individual freedom 

 and liberty of action, and the certainty and precision of 

 their united employment. 



In the condition of bodily rest the extent of its 

 movements or circulation is reduced to a minimum ; in 

 the condition of bodily activity, however, the extent and 

 range of these movements must be great, according to the 

 violence and duration of that activity ; but under the 

 combined influences of bodily activity and mental excite- 

 ment a pitch of cyclonic, or tornado, violence of movement 

 may be reached to which there is scarcely a limit. This 

 therefore necessitates the provision of a system of circula- 

 tory vessels equal to the strain, whose function will be 

 primarily that of circulation, and secondarily that of 

 protecting the central and enclosed nervous system in all 

 its parts from the effects of that violence. 



" Excretion " from the cerebro-spinal cavity of the 

 effete materials collected hither from the neuroglial and 

 nerve structures, consisting of nerve debris or " brain 

 sweat," and the " thousands upon thousands " of outcast 

 atoms from cell and tube and fibre which constitute the 



