I 
300 Mr. Bell on the nerves which associate the muscles 
matter is embraced between the anterior and posterior virgce 
of that body, and that this portion may be traced down- 
wards between the roots of the spinal nerves. From the 
upper part of this column, where it begins in the medulla 
oblongata, the several nerves proceed which have formed the 
subject of these papers, and on the influence of which, it has 
been proved, the motions of respiration principally depend. 
It is not an extravagant conclusion to say farther, that the 
power of the regular succession of intercostal and lumbar 
nerves, as far as they regulate the respiratory actions, pro- 
ceeds from the connections of the roots of these nerves with 
this column, which is continued downwards, and which can 
throughout be distinguished from the rest of the spinal 
marrow. 
We are now enabled to distinguish the influence of the 
spinal marrow and its regular succession of nerves, from 
those which have been traced in these papers. The first are 
essential to the act of respiration ; without them the others 
are unequal to the task. But on the other hand, although 
the regular succession of spinal nerves be equal to the raising 
and depressing the thorax, they are not competent to the 
performance of the motions of the glottis, pharynx, lips, and 
nostrils, which several parts are necessarily influenced in ex- 
cited respiration, as well as in the acts of smelling, coughing, 
sneezing, and speaking : for these, the co-operation of the 
whole extended class of respiratory nerves is required. 
Surveying the complicated machinery which in man is pre- 
pared for these various offices, we may reap the benefit of 
these fatiguing details, in the contemplation of the most in- 
teresting phenomena in nature. The relations of the subject 
