of the chest in breathing, speaking, and expression. 297 
in their office ; and, although the regular system of nerves 
refused acting, the sterno-mastoideus and the trapezius partook 
of their share in the act of respiration. Seeing that the mas- 
toid muscle has two sets of nerves, that one of these is of the 
class of voluntary nerves, and the other of respiratory nerves, 
are we not borne out in concluding, that when the head is 
moved, being a voluntary act strictly, it is performed through 
the common class of voluntary nerves ? that when the chest 
is raised, it is an act of respiration, and is affected through 
those nerves which controul the muscles in respiration ? 
This conclusion is confirmed by the following experiment. 
In the ass, there are two muscles which take the office of the 
mastoid muscle ; one is inserted into the jaw, which we may 
call sterno-maxillaris , and the other into the vertebrae, viz. 
sterno-vertebralis. To these the superior respiratory nerve 
(or spinal accessory) is distributed in its passage to the tra- 
pezius. These muscles are at the same time supplied with 
numerous nerves directly from the spinal marrow. If we 
expose the superior respiratory nerve, and then induce excited 
respiration, so as to bring these muscles into powerful action 
in combination with the other muscles of respiration, and if, 
while this action is performed, we divide the nerve, the mo- 
tion ceases, and the muscle remains relaxed until the animal 
brings it into action as a voluntary muscle. 
An ass being thrown, its phrenic nerves were divided, on 
which a remarkable heaving of the chest took place. It rose 
higher, and the margins of the chest were more expanded at 
each inspiration. There was no particular excitement of the 
muscles of the neck, shoulder, or throat, at this time; so 
mdcccxxii. Oq 
