translator's introduction. xi 



" xxxvii. Function of the common Sensorium. 



"§ 215. That point of the nervous system is termed the common 

 sensorium (Sensorium commune), in which external impressions meet, 

 and from which internal impressions are diffused to all parts of our 

 body ; in which, consequently, the consensus of the nerves takes place 

 that is necessary to Life, and in which external impressions are reflected 

 into internal impressions, according to the law of self-conservation 

 (178), with, or without, consciousness. 



"§ 216. That sensorium in which impressions are reflected with 

 the consciousness of the soul, may be termed the soul-sensorium ; and 

 the other, the corporeal sensorium ; just as Willis has already divided 

 it, into the rational and the corporeal soul. 



"§ 217. The brain, only, is the seat of the soul-sensorium; the 

 seat of the body-sensorium is the brain, spinal cord, and (as all obser- 

 vation shows) the ganglia and plexuses of the nerves. That external 

 impressions can also be reflected in the brain, without conscious- 

 ness, is shown by the involuntary convulsions of voluntary muscles. 

 Monsters, born without brain and spinal cord, and which live up to 

 the moment of birth, show that the consensus of the nerves necessary 

 to this form of life, imperfect though it be, may take place, and that 

 there may be a corporeal sensorium independently of the brain and 

 spinal cord, and which, consequently, must be constituted by the 

 plexuses and ganglia of the nerves. The movements observed to take 

 place on irritating the nerves of a headless frog, and seen also in 

 decapitated men, prove the same thing. The sympathetic nerve ap- 

 pears likewise to reflect its impressions in its ganglia and plexuses, 

 without the consciousness of the soul. 



" § 218. In accordance with this consensus of the nerves, as well 

 in the brain as in the spinal cord, ganglia, and plexuses, the operation 

 of a stimulus is not limited to the nerves immediately irritated, but is 

 extended to distant nerves, in known or unknown connection with the 

 irritated nerves ; and this is demonstrated by innumerable examples of 

 consensus of nerves [consensus nervorum], as, for instance, the irri- 

 tation in the pregnant uterus often causes nausea, vomiting, headache, 

 toothache, &c. 



" § 219. Both the soul-sensorium and body-sensorium operate ac- 

 cording to the law of self-conservation (178), a truth which may be 

 illustrated by numerous examples. For instance, the irritation or 

 impression of too strong a light goes to the optic nerve, from whence 

 it can only get at the ciliary nerves through the brain, and induce 



