252 
SIR CHARLES BELL ON THE NERVOUS SYSTEM. 
ing’ towards the origin of the nerve, to be returned by parallel nerves upon the mus- 
cles : for the uniformity of nature’s laws is maintained in both the great systems, the 
regular, and the respiratory. 
Experiments countenance another early conclusion. Of the three conspicuous 
nerves of this system which have been associated under the name of the eighth pair 
of nerves, the spinal accessory nerve is proved to be the essential muscular nerve. 
The experiments of Professor Muller, Drs. Reid and Valentin, exhibit this nerve as 
purely muscular. 
I drew this conclusion when I presented to the Society the plan of the respiratory 
nerves and muscles. I suggested that the roots of the spinal accessory nerve and of 
the diaphragmatic nerve arose from the same portion of nervous matter : and that 
whilst the one went directly, and by the shortest way to the diaphragm, the other 
proceeded upwards, entered the head, and came down in association with the other 
nerves, in order, by these communications, to unite the motions of the air-tubes with 
the play of the chest in respiration, and that the whole respiratory apparatus might 
consent in action. Often as I have set my young friends to determine the question 
by dissection, I have found them puzzling and giving up the pursuit. No doubt the 
dissection is difficult ; and we must still rest satisfied with a process of reasoning. 
The influence of these nerves is necessary to each other. The muscles of the chest 
and the diaphragm continue in action when the motions of the arm and of the muscles 
of the neck are lost. These nerves and their respective muscles continue in office 
when both sense and motion are gone. 
In making two distinct systems of the nerves arising from the spinal column, it 
was never my intention that it should be believed that they were cut off from the 
sensorium. The connexion of the brain with the spinal marrow is a distinct subject 
of inquiry. 
We know that concatenated motions can be excited in the body where there is no 
brain. We know that the action of respiration will continue when the brain is taken 
away ; so far, then, it is obvious that the relations of the frame, whether for the pur- 
pose of locomotion and action, or of breathing, are perfect, independently of cerebrum 
and cerebellum. The question remains, what is the nature of that relation, or of that 
influence, maintained by the brain over the nervous system of the body ? However 
that connexion may hereafter be found to be established, it will not invalidate the 
conclusions as to the unity of office of the nerves employed in respiration, and in the 
actions where the respiratory apparatus is brought into play. 
Before concluding this subject, it is pertinent to notice, that writers have been led 
to attribute the entire action of respiration to the sensation in the lungs. To a cer- 
tain degree this is undoubtedly true. When I formerly stated, that upon dividing 
the par vagum (and with it the sympathetic nerve), and cutting through the spinal 
marrow, the act of respiration continued, I established the fact that there was a source 
of motion in the respiratory organs independently of any sensation in the lungs. I 
