THE GREAT SPINAL ORGANIC NERVE. 
265 
concerned with ingestion or egestion, or some of the vital func- 
tions of life : the system is connected with these chiefly, or 
these alone. In the act of ordinary breathing the filaments of 
the par vagum are excited by the contact of a certain portion of 
carbonic acid in the lungs : that excitation is conveyed to the me- 
dulla oblongata; and the medulla oblongata combines the actions 
of certain muscles under its control, and by their joint influence 
the cavity of the chest is contracted and the carbonic acid ex- 
pelled. 
I have little objection to this system, so far as I am enabled to un- 
derstand it. The plain matter of fact is, that a system of nervous 
energy, of which our predecessors had somewhat confused ideas, 
has been introduced among us, and based on the surest ground, that 
of anatomy and physiological experiment. There are in the spi- 
nal cord two perfectly distinct yet allied systems of nervous ac- 
tion, that which relates to our connexion with things around us, 
and that which is connected with life itself ; and it matters little 
whether we call the one the animal and the other the organic sys- 
tem, or whether we distinguish the one by the title of the sentient 
and voluntary , and the other the excitor and motory powers. 
And now r , gentlemen, we arrive at the point whence we just now 
started. In the functions of respiration and digestion which we 
have lately considered we have traced the energy of the vital 
powers connected with the medulla oblongata in the first instance. 
A portion of the respiratory apparatus, as had been sufficiently il- 
lustrated in former lectures, was under the influence of the se- 
venth nerve — the portio dura of the seventh, according to the 
old distribution — many of the muscles of the face were involun- 
tarily and unconsciously engaged in the common process of 
breathing, both under circumstances of health and disease. From 
a lower part of the medulla oblongata sprung the glosso-pharyn- 
geal nerve, combining other of the muscles of the face and of the 
throat. The influence of the vagal nerves was traced in the la- 
rynx, the trachea, the bronchi, the general structure and func- 
tion of the lungs — and in the first and important processes too of 
digestion — in the motions of the pharynx, the oesophagus, the 
stomach, and the first intestine — and there, so far as the medulla 
oblongata was concerned, the influence of the organic nerves 
plainly and altogether ceased. In the latter portion of the present 
lecture, when the medulla oblongata was acting no more, the 
principle of organic life is not lost, but a similar power exists in 
other portions of the spinal cord ; we trace it in the function of 
the spinal accessory nerve — the phrenic nerve — the exterior re- 
spiratory — the intercostals, the lumbar, the abdominal nerves. 
They are no longer, as perhaps we had carelessly imagined, or 
