254 THE EXCITO-MOTORY SYSTEM OF NERVES. 
This excito-motory system of nerves presides over ingestion 
and exclusion, over retention and egestion, and over the orifices 
and sphincters of the animal frame. It is, therefore, the nervous 
system of respiration and deglutition, and of the retention and 
expulsion of the faeces and urine, and of the semen. 
By means of this system, that to 2 irbiilon” of the ingesta 
and egesta, so beautifully and eloquently described by Cuvier, is 
effected. By means of this system, the animal frame is consti¬ 
tuted a casket, guarded at the upper part, and securely closed at 
the lower. The excito-motory, or true spinal system, is the ner¬ 
vous agent in all those motions hitherto confessedly not under¬ 
stood, by the fact of their being designated by the unmeaning 
term sympathetic, See. 
This system is also the source of tone in the whole muscular 
system. 
The true spinal system is, in a peculiar sense, the seat or nervous 
agent of the appetites and passions. Through it the emotions 
effect not the expressions of the countenance and the respiration 
alone, but the pharynx, the larynx, the sphincters, the expulsors, 
and indeed the whole muscular system of the animal frame. 
The true spinal system is susceptible of modification by volition, 
and, on this account, some of its functions have been denomi¬ 
nated mixed. It is, also, constantly under a certain influence of 
the volition, as is manifest in the difference in the respiration, 8cc. 
during intense mental attention, sleep, and coma, and in ordinary 
circumstances. 
The true spinal system never sleeps ; respiration and deglutition, 
and the action of the orifices and sphincters, are continued. 
That a principle so extensive and important in the animal 
ecojiomy should not have been detected and known before, must 
appear extraordinary; and that such is the fact, may be demon¬ 
strated by considering the most simple and familiar examples of 
the functions over which this principle presides. Has it been 
stated in any work, antient or modern, that the deglutition of 
water by the pharynx, the exclusion of carbonic acid by the 
larynx, the retention of the urine and faeces by the sphincters, are 
exclusively functions of the spinal marrow, and of a peculiar system 
of excitor and motor nerves, of which it is the centre, or axis ? 
Nay, the idea of a system of excitor nerves, constantly operating 
on the animal economy, preserving its orifices open, its sphincters 
closed, and constituting the primum mobile of the important 
function of respiration, I believe to be new. The acts are so 
familiar to us, that we have thought them understood, when the 
nervous agents through which they have been excited have not 
even been detected ; yet, that this view is the true one, is proved 
by the most decisive experiments. 
