270 INFLUENCE OF THE CIRCULATION 



2. That the recognised necessity for that con- 

 stant maintenance of the cerebral circulation, as a 

 condition indispensable to the exercise of its mental 

 functions, applies to the white as much as to the 

 gray matter of the brain. 



3. That the transmission of sensorial impressions 

 along the cerebro-spinal nerves is a purely vital 

 action, and, as such, quite distinct in its nature and 

 in the laws regulating it, from the quasi -physical 

 force producing excito-motory phenomena. 



4. That, as regards their sensorial functions, the 

 cerebro-spinal nerves are to be regarded as not only 

 anatomically, but physiologically and pathologically, 

 identical with the white or fibrous portion of the 

 brain, and, consequently, as liable to the same phy- 

 sico-vital sources of disordered action as the brain 

 itself. 



In attempting to establish any law explanatory of 

 the mysterious operations of the nervous system, it 

 is above all things essential to discard pre-conceived 

 ideas, and reason solely from facts. And, fortunately, 

 the phenomena demonstrating the truth of the former 

 of the two principal laws above stated, namely, the 

 dependence of the sensorial functions of the nerves 

 on the incessant circulation of the blood in the ad- 

 jacent vessels, are so clear, direct, and adducible, as 

 to render it wholly incontrovertible. 



It has for many years been known that when a 

 ligature is tightly applied to the abdominal aorta of 

 any of the Mammalia, the hinder extremities an 

 instantly paralysed. This circumstance was first 

 noticed in experiments on animals ; and, in tin- 



