ns, which latter,
when divided, will trammel the operation by the copious haemorrhage
which all veins at this region of the neck are prone to supply, owing to
their direct communication with the main venous trunks of the heart; and
not unfrequently the inferior thyroid artery overlies the trachea at the
point D, Plate 9, when this thyroid vessel arises directly from the arch
of the aorta, between the roots of the innominate and left common
carotid, or when it springs from the innominate itself. The inferior
thyroid vein, sometimes single and sometimes double, overlies the
trachea at the point D, Plate 9, when this vein opens into the left
innominate venous trunk, as this latter crosses over the root of the
main arteries springing from the aorta.

Laryngotomy is, anatomically considered, a far less dangerous operation
than tracheotomy, for the above-named reasons; and the former should
always be preferred when particular circumstances do not render the
latter operation absolutely necessary. In addition to the fact, that the
carotid arteries lie farther apart from each other and from the median
place--viz., the crico-thyroid interval, which is the seat of
laryngotomy--than they do lower down on either side of the trachea, it
should also be noticed that the tracheal tube being more moveable than
the larynx, is hence more liable to swerve from the cutting instrument,
and implicate the vessels. Tracheotomy on the infant is a far more
anxious proceeding than the same operation performed on the adult;
because the trachea in the infant's body lies more closely within the
embrace of the carotid arteries, is less in diameter, shorter, and more
mobile than in the adult body.

The episternal or interclavicular region is a locality traversed by so
many vitally important structures gathered together in a very limited
space, that all operations which concern this region require more steady
caution and anatomical knowledge than most surgeons are bold enough to
test their possession of. The reader will (on comparing Plates 9 and 10)
be enabled to take account of those structures which it is necessary to
divide in the operation required for ligaturing the innominate artery,
A, Plate 9, or either of those main arterial vessels (the right common
carotid and subclavian) which spring from it; and he will also observe
that, although the same number and kind of structures overlie the
carotid and subclavian vessels, A B, of the left side, Plat