SIR CHARLES BELL ON THE NERVOUS SYSTEM. 
249 
The Society must perceive, that when it was demonstrated that the anterior and 
posterior roots differed in function, the whole investigation became anatomical. 
Tracing the column of the spinal marrow which gives rise to the anterior roots, 
upwards, we meet with the ninth, sixth, and third, arising from the same tract ; and 
as these are distributed to muscles exclusively, we must infer that they are motor 
nerves; thus confirming the deductions from the experiments, that the whole ante- 
rior column gives off only nerves of motion. 
It must likewise be obvious how these investigations into the functions of the spinal 
nerves, their roots and columns, carried me back to the original field of inquiry, the 
cerebral nerves ; and this conducted me to the observation, that the fifth pair of the 
brain is analogous, in the structure of its roots, and its functions, to the spinal nerves. 
The next subject to which I request the indulgent attention of the Society, regards 
those nerves, which in a paper delivered in 1 82 1 , I called 
The Respiratory System of Nerves. 
I foresaw that my views on this subject would prove embarrassing to physiologists. 
But the length of time that has elapsed, and the ingenuity of many men who have 
engaged in the investigation, have made it ripe for further inquiry. 
In the paper alluded to, certain nerves, very distinct from the thirty spinal nerves 
and fifth pair, which from their uniformity of origin and course I called regular 
nerves, were pointed out. These nerves also bore distinct features from the nerves of 
the encephalon. They were the portio dura of the seventh nerve, the glossopharyn- 
geal nerve, and the spinal accessory nerve ; to which I added the diaphragmatic, and 
external respiratory nerve. 
As these nerves are peculiar in their origins, so are they in their course and distri- 
bution. On the outside of the corpus olivare, and anterior to the processus ad cere- 
bellum , when the pia mater is torn away, a tract, marked by the size of the holes 
from which the nourishing vessels have been withdrawn, and continued downwards 
behind the ligamenta denticulata, is perceived ; from the upper part of this column 
these nerves arise conspicuously, and from this they diverge as from a centre. They 
differ in length, and perhaps in importance ; but they go to every part, throughout 
the extended frame, associated in the act of respiration, or in the many lesser actions 
in which the organs of respiration participate. 
Another circumstance was pointed out as marking their peculiarity. When sense 
and volition are lost, and the individual is dying, these nerves retain their power, and 
are the last to yield to the influence of death. 
In marking the difference in these nerves from the regular spinal nerves and fifth 
pair, we may add to their peculiar mode of origin, the distinction in the columns from 
which they arise. The peculiarity of the columns which give origin to the regular 
nerves is their decussations : but such decussations are not found in the columns 
which give off the respiratory nerves. 
MDCCCXL. 2 K 
