e upper
part of the spinal cord. Hence it is sometimes named the respiratory
column. These nerves are distributed to one of the muscles of the eye;
to the muscles of the face; to the tongue, pharynx, oesophagus,
stomach, heart, lungs, diaphragm, and some of the muscles of the neck
and chest.

785. It is through the instrumentality of the accessory, phrenic,
and external respiratory nerves, (10, 11, 12, 13, fig. 132,) that
the muscles employed in respiration are brought into action without
the necessity of the interference of the mind. Though to a certain
extent they may be under the influence of the will, yet it is only in
a secondary degree. No one can long suspend the movements of
respiration;[20] for in a short time, instinctive feeling issues
its irresistible mandate, which neither requires the aid of erring
wisdom, nor brooks the capricious interference of the will.

[20] Dr. Elliotson, and some other writers On physiology, have
detailed cases of death from voluntary suspension of respiration.
But these cases are not conclusive, as examinations were not
made, so as to determine positively, that death did not result
from disease of the heart, brain, or some other vital organ.

[Illustration: Fig. 132. The distribution of the respiratory nerves. _a_,
Section of the brain and medulla oblongata. _b_, The lateral columns of
the spinal cord. _c_, _c_, The respiratory tract of the spinal cord. _d_,
The tongue. _e_, The larynx. _f_, The bronchia. _g_, The oesophagus. _h_,
The stomach. _i_, The diaphragm. 1, The pneumogastric nerve. 2, The
superior laryngeal nerve. 3, The recurrent laryngeal nerve. (These two
ramify on the larynx.) 4, The pulmonary plexus of the tenth nerve. 5, The
cardiac plexus of the tenth nerve. These two plexuses supply the heart
and lungs with nervous filaments. 7, The origin of the fourth pair of
nerves, that passes to the superior oblique muscle of the eye. 8, The
origin of the facial nerve, that is spread out on the side of the face
and nose. 9, The origin of the glosso-pharyngeal nerve, that passes to
the tongue and pharynx. 10, The origin of the spinal accessory nerve. 11,
This nerve penetrating the sterno-mastoideus muscle. 12, The origin of
the internal respiratory or phrenic nerve, that is seen to ramify on the
diaphragm. 13, The origin of the external respiratory nerve, that
ramifies on the pectoral and scaleni muscles.]

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784. Gi