aftercoming necessities modify and distort in some degree. The spaces
occupied by the opposite lungs in the adult body do not exactly
correspond as to capacity, O O, Plate 1. Neither is the cardiac space, A
E G D, Plate 1, which is traversed by the common median line,
symmetrical. The asymmetry of the lungs is mainly owing to the form and
position of the heart; for this organ inclines towards the left thoracic
side. The left lung is less in capacity than the right, by so much space
as the heart occupies in the left pulmonary side. The general form of
the thorax is that of a cone, I I N N, Plate 1, bicleft through its
perpendicular axis, H M. The line of bicleavage is exactly median, and
passes through the centre of the sternum in front, and the centres of
the dorsal vertebral behind. Between the dorsal vertebral and the
sternum, the line of median cleavage is maintained and sketched out in
membrane. This membranous middle is formed by the adjacent sides of the
opposite pleural or enveloping bags in which the lungs are enclosed. The
heart, A, Plate 1, is developed between these two pleural sacs, F F, and
separates them from each other to a distance corresponding to its own
size. The adjacent sides of the two pleural sacs are central to the
thorax, and form that space which is called mediastinum; the heart is
located in this mediastinum, U E, Plate 1. The extent of the thoracic
region ranges perpendicularly from the root of the neck, Q, Plate 1, to
the roof of the abdomen--viz., the diaphragm, P, transversely from the
ribs of one side, I N, Plate 1, to those of the other, and
antero-posteriorly from the sternum, H M, to the vertebral column. All
this space is pulmonary, except the cardiac or median space, which, in
addition to the heart, A, Plate 1, and great bloodvessels, G C B,
contains the oesophagus, bronchi, &c. The ribs are the true enclosures
of thoracic space, and, generally, in mammalian forms, they fail or
degenerate at that region of the trunk which is not pulmonary or
respiratory. In human anatomy, a teleological reason is given for
this--namely, that of the ribs being mechanically subservient to the
function of respiration alone. But the transcendental anatomists
interpret this fact otherwise, and refer it to the operation of a higher
law of formation.
The capacity of the thorax is influenced by the capacity of the abdomen
and its contents. In order to admit of full inspiration and pulmonary
expansion, the abdominal viscera recede in the same ratio as the lungs
dilate. The diaphragm, P P, Plate 1, or transverse musculo-membranous
partition which divides the pulmonary and alimentary cavities, is, by
virtue of its situation, as mechanically subservient to the abdomen as
to the thorax. And under general notice, it will appear that even the
abdominal muscles are as directly related to the respiratory act as
those of the thorax. The connexion between functions is as intimate and
indissoluble as the connexion between organs in the same body. There can
be no more striking proof of the divinity of design than by such
revelations as anatomical science everywhere manifests in facts such as
this--viz., that each organ serves in most cases a double, and in many a
triple purpose, in the animal economy.
The apex of the lung projects into the root of the neck, even to a
higher level, Q, Plate 1, than that occupied by the sternal end of the
clavicle, K. If the point of a sword were pushed through the neck above
the clavicle, at K, Plate 1, it would penetrate the apex of the right
lung, where the subclavian artery, Q, Plate 1, arches over it. In
connexion with this fact, I may mention it as very probable that the
bruit, or continuous murmur which we hear through the stethoscope, in
chlorotic females, is caused by the pulsation of the subclavian artery
against the top of the lung. The stays or girdle which braces the loins
of most women prevents the expansion of the thoracic apparatus,
naturally attained by the descent of the diaphragm; and hence, no doubt,
the lung will distend inordinately above towards the neck. It is an
interesting fact for those anatomists who study the higher
generalizations of their science, that at those very localities--viz.,
the neck and loins, where the lungs by their own natural effort are
prone to extend themselves in forced inspiration--happen the "anomalous"
creations of cervical and lumbar ribs. The subclavian artery is
occasionally complicated by the presence of these costal appendages.
If the body be transfixed through any one of the intercostal spaces, the
instrument will surely wound some part of the lung. If the thorax be
pierced from any point whatever, provided the instrument be directed
towards a common centre, A, Plate 1, the lung will suffer lesion; for
the heart is, almost completely, in the healthy living body, enveloped
in the lungs. So true is it that all the costal region (the asternal as
well as the sternal) is a pulmonary enclosure, that any instrument which
pierces intercostal space must wound the lung.
As the sternal ribs degenerate into the "false" asternal or incomplete
ribs from before, obliquely backward down to the last dorsal vertebra,
so the thoracic space takes form. The lungs range through a much larger
space, therefore, posteriorly than they do anteriorly.
The form of the thorax, in relation to that of the abdomen, may be
learned from the fact that a gunshot, which shall enter a little below
N, Plate 1, and, after traversing the body transversely, shall pass out
at a corresponding point at the opposite side, would open the thorax and
the abdomen into a common cavity; for it would pierce the thorax at N,
the arching diaphragm at the level of M, and thereat enter the belly;
then it would enter the thorax again at P, and make exit below N,
opposite. If a cutting instrument were passed horizontally from before
backward, a little below M, it would first open the abdomen, then pierce
the arching diaphragm, and pass into the thorax, opposite the ninth or
eighth dorsal vertebra.
The outward form or superficies masks in some degree the form of the
interior. The width of the thorax above does not exceed the diameter
between the points I I, of Plate 1, or the points W W, of Plate 2. If we
make percussion directly from before backwards at any place external to
I, Plate 1, we do not render the lung vibrative. The diameters between I
I and N N, Plate 1, are not equal; and these measures will indicate the
form of the thorax in the living body, between the shoulders above and
the loins below.
The position of the heart in the thorax varies somewhat with several
bodies. The size of the heart, even in a state of perfect health, varies
also in subjects of corresponding ages, a condition which is often
mistaken for pathological. For the most part, its form occupies a space
ranging from two or three lines right of the right side of the sternum
to the middle of the shafts of the fifth and sixth ribs of the left
side. In general, the length of the osseous sternum gives the exact
perpendicular range of the heart, together with its great vessels.
The aorta, C, Plates 1 and 2, is behind the upper half of the sternum,
from which it is separated by the pericardium, D, Plate 1, the thin edge
of the lung, and the mediastinal pleurae, U E, Plate 1, &c. If the heart
be injected from the abdominal aorta, the aortal arch will flatten
against the sternum. Pulmonary space would not be opened by a
penetrating instrument passed into the root of the neck in the median
line above the sternum, at L, Plate 1. But the apices of both lungs
would be wounded if the same instrument entered deeply on either side of
this median line at K K. An instrument which would pierce the sternum
opposite the insertion of the second, third, or fourth costal cartilage,
from H downwards, would transfix some part of the arch of the aorta, C,
Plate 1. The same instrument, if pushed horizontally backward through
the second, third, or fourth interspaces of the costal cartilages close
to the sternum, would wound, on the right of the sternal line, the vena
cava superior, G, Plate 1; on the left, the pulmonary artery, B, and
the descending thoracic aorta. In the healthy living body, the thoracic
sounds heard in percussion, or by means of the stethoscope, will vary
according to the locality operated upon, in consequence of the variable
thickness of those structures (muscular and osseous, &c.,) which invest
the thoracic walls. Uniformity of sound must, owing to these facts, be
as materially interrupted, as it certainly is, in consequence of the
variable contents of the cavity. The variability of the healthy thoracic
sounds will, therefore, be too often likely to be mistaken for that of
disease, if we forget to admit these facts, as instanced in the former
state. Considering the form of the thoracic space in reference to the
general form of the trunk of the living body, I see reason to doubt
whether the practitioner can by any boasted delicacy of manipulation,
detect an abnormal state of the pulmonary organs by percussion, or the
use of the stethoscope, applied at those regions which he terms
coracoid, scapulary, subclavian, &c., if the line of his examination be
directed from before backwards. The scapula, covered by thick carneous
masses, does not lie in the living body directly upon the
osseous-thorax, neither does the clavicle. As all antero-posterior
examination in reference to the lungs external to the points, I I,
between the shoulders cannot, in fact, concern the pulmonary organs, so
it cannot be diagnostic of their state either in health or disease. The
difficulties which oppose the practitioner's examination of the state of
the thoracic contents are already numerous enough, independent of those
which may arise from unanatomical investigation.
DESCRIPTION OF PLATES 1 & 2.
PLATE 1.
A. Right ventricle of the heart.
B. Origin of pulmonary artery.
C. Commencement of the systemic aorta, ascending part of aortic arch.
D. Pericardium investing the heart and the origins of the great
bloodvessels.
E. Mediastinal pleura, forming a second investment for the heart,
bloodvessels, &c.
F. Costal pleura, seen to be continuous above with that which forms
the mediastinum.
G. Vena cava superior, entering pericardium to join V, the right
auricle.
H. Upper third of sternum.
I I. First ribs.
K K. Sternal ends of the clavicles.
L. Upper end of sternum.
M. Lower end of sternum.
N N. Fifth ribs.
O O. Collapsed lungs.
P P. Arching diaphragm.
Q. Subclavian artery.
R. Common carotid artery, at its division into internal and external
carotids.
S S. Great pectoral muscles.
T T. Lesser pectoral muscles.
U. Mediastinal pleura of right side.
V. Right auricle of the heart.
[Illustration: Upper body, showing internal organs of neck and chest.]
Plate 1
PLATE 2.
A. Right ventricle of the heart. A a. Pericardium.
B. Pulmonary artery. B b. Pericardium.
C. Ascending aorta. C c. Transverse aorta.
D. Right auricle.
E. Ductus arteriosus in the loop of left vagus nerve, and close to
phrenic nerve of left side.
F. Superior vena cava.
G. Brachio-cephalic vein of left side.
H. Left common carotid artery.
I. Left subclavian vein.
K. Lower end of left internal jugular vein.
L. Right internal jugular vein.
M. Right subclavian vein.
N. Innominate artery--brachio-cephalic.
O. Left subclavian artery crossed by left vagus nerve.
P. Right subclavian artery crossed by right vagus nerve, whose inferior
laryngeal branch loops under the vessel.
Q. Right common carotid artery
R. Trachea.
S. Thyroid body.
T. Brachial plexus of nerves.
U. Upper end of left internal jugular vein.
V V. Clavicles cut across and displaced downwards.
W W. The first ribs.
X X. Fifth ribs cut across.
Y Y. Right and left mammae.
Z. Lower end of sternum.
[Illustration: Upper body, showing internal organs of neck and chest.]
Plate 2
COMMENTARY ON PLATES 3 & 4.
THE SURGICAL FORM OF THE SUPERFICIAL CERVICAL AND FACIAL
REGIONS, AND THE RELATIVE POSITION OF THE PRINCIPAL
BLOOD-VESSELS, NERVES, &c.
When the neck is extended in surgical position, as seen in Plates 3 and
4, its general outline assumes a quadrilateral shape, approaching to a
square. The sides of this square are formed anteriorly by the line
ranging from the mental symphysis to the top of the sternum, and
posteriorly by a line drawn between the occiput and shoulder. The
superior side of this cervical square is drawn by the horizontal ramus
of the lower maxilla, and the inferior side by the horizontal line of
the clavicle. This square space, R 16, 8, 6, Plate 4, is halved by a
diagonal line, drawn by the sterno-cleido-mastoid muscle B, which cuts
the square into two triangles. In the anterior triangle, F 16, 6, Plate
4, is located the superficial common carotid artery, C, and its
branches, D, with accompanying nerves. In the posterior triangle, 9, 8,
6, Plate 4, is placed the superficial subclavian artery, A, its
branches, L M, and the brachial plexus of nerves, I. Both these
triangles and their contents are completely sheathed by that thin
scarf-like muscle, named platysma myoides, A A, Plate 3, the fibres of
which traverse the neck slantingly in a line, O A, of diagonal direction
opposite to and secant of that of the sterno-mastoid muscle.
When the skin and subcutaneous adipose membrane are removed by careful
dissection from the cervical region, certain structures are exposed,
which, even in the undissected neck, projected on the superficies, and
are the unerring guides to the localities of the blood-vessels and
nerves, &c. In Plate 4, the top of the sternum, 6; the clavicle, 7; the
"Pomum Adami," 1; the lower maxilla at V; the hyoid bone, Z; the
sterno-cleido-mastoid muscle, B; and the clavicular portion of the
trapezius muscle, 8; will readily be felt or otherwise recognised
through the skin, &c. When these several points are well considered in
their relation to one another, they will correctly determine the
relative locality of those structures--the blood-vessels, nerves, &c.,
which mainly concern the surgical operation.
The middle point, between 7, the clavicle, and 6, the sternum, of Plate
4, is marked by a small triangular space occurring between the
clavicular and sternal divisions of the sterno-cleido-mastoid muscle.
This space marks the situation (very generally) of the bifurcation of
the innominate artery into the subclavian and common carotid arteries of
the right side; a penetrating instrument would, if passed into this
space at an inch depth, pierce first the root of the internal jugular
vein, and under it, but somewhat internal, the root of either of these
great arterial vessels, and would wound the right vagus nerve, as it
traverses this region. For some extent after the subclavian and carotid
vessels separate from their main common trunk, they lie concealed
beneath the sterno-mastoid muscle, B, Plate 4, and still deeper beneath
the sternal origins of the sterno-hyoid muscle, 5, and sterno-thyroid
muscle, some of whose fibres are traceable at the intervals. The
omo-hyoid muscle and the deep cervical fascia, as will be presently seen,
conceal these vessels also.
The subclavian artery, A, Plate 4, first appears superficial to the
above-named muscles of the cervical region just at the point where,
passing from behind the scalenus muscle, N, Plate 4, which also conceals
it, it sinks behind the clavicle. The exact locality of the artery in
this part of its course would be indicated by a finger's breadth
external to the clavicular attachment of the sterno-mastoid muscle. The
artery passes beneath the clavicle at the middle of this bone, a point
which is indicated in most subjects by that cellular interval occurring
between the clavicular origins of the deltoid and great pectoral
muscles.
The posterior cervical triangle, 9, 8, 7, Plate 4, in which the
subclavian artery is situated, is again subdivided by the muscle
omo-hyoid into two lesser regions, each of which assumes somewhat of a
triangular shape. The lower one of these embraces the vessel, A, and
those nerves of the brachial plexus, I, which are in contact with it.
The posterior belly of the omo-hyoid muscle, K, and the anterior
scalenus muscle, N, form the sides and apex of this lesser triangular
space, while the horizontal clavicle forms its base. This region of the
subclavian artery is well defined in the necks of most subjects,
especially when the muscles are put in action. In lean but muscular
bodies, it is possible to feel the projection of the anterior scalenus
muscle under the skin, external to the sterno-mastoid. The form of the
omo-hyoid is also to be distinguished in the like bodies. But in all
subjects may be readily recognised that hollow which occurs above the
clavicle, and between the trapezius, 8, and the sterno cleido-mastoid, 7
B, in the centre of which hollow the artery lies.
The contents of the larger posterior cervical triangle, formed by B, the
sterno-mastoid before; 9, the splenius; and 8, the trapezius behind,
and by the clavicle below, are the following mentioned structures--viz.,
A, the subclavian artery, in the third part of its course, as it emerges
from behind N, the scalenus anticus; L, the transversalis colli artery,
a branch of the thyroid axis, which will be found to cross the
subclavian vessel at this region; I, the brachial plexus of nerves,
which lie external to and above the vessel; H, the external jugular
vein, which sometimes, in conjunction with a plexus of veins coming from
behind the trapezius muscle, entirely conceals the artery; M, the
posterior scapular artery, a branch of the subclavian, given off from
the vessel after it has passed from behind the scalenus muscle; O,
numerous lymphatic glands; P, superficial descending branches of the
cervical plexus of nerves; and Q, ascending superficial branches of the
same plexus. All these structures, except some of the lymphatic glands,
are concealed by the platysma myoides A, as seen in Plate 3, and beneath
this by the cervical fascia, which latter shall be hereafter more
clearly represented.
In somewhat the same mode as the posterior half of the omo-hyoid
subdivides the larger posterior triangle into two of lesser dimensions,
the anterior half of the same muscle divides the anterior triangle into
two of smaller capacity.
The great anterior triangle, which is marked as that space inclosed
within the points, 6, the top of the sternum, the mental symphysis and
the angle of the maxilla; and whose sides are marked by the median line
of the neck before, the sterno-mastoid behind, and the ramus of the jaw
above, contains C, the common carotid artery, becoming superficial from
beneath the sterno-mastoid muscle, and dividing into E, the internal
carotid, and D, the external carotid. The anterior jugular vein, 3, also
occupies this region below; while some venous branches, which join the
external and internal jugular veins, traverse it in all directions, and
present obstacles to the operator from their meshy plexiform arrangement
yielding, when divided, a profuse haemorrhage.
The precise locality at which the common carotid appears from under the
sterno-mastoid muscle is, in almost all instances, opposite to the
thyroid cartilage. At this place, if an incision, dividing the skin,
platysma and some superficial branches of nerves, be made along the
anterior border of the sterno-mastoid muscle, and this latter be turned
a little aside, a process of cervical fascia, and beneath it the sheath
of the carotid artery, will successionally disclose themselves. In many
bodies, however, some degree of careful search requires to be made prior
to the full exposure of the vessel in its sheath, in consequence of a
considerable quantity of adipose tissue, some lymphatic glands, and many
small veins lying in the immediate vicinity of the carotid artery and
internal jugular vein. This latter vessel, though usually lying
completely concealed by the sterno-mastoid muscle, is frequently to be
seen projecting from under its fore part. In emaciated bodies, where the
sterno-mastoid presents wasted proportions, it will, in consequence,
leave both the main blood-vessels uncovered at this locality in the
neck.
The common carotid artery ascends the cervical region almost
perpendicularly from opposite the sterno-clavicular articulation to the
greater cornu of the os hyoides. For the greater part of this extent it
is covered by the sterno-mastoid muscle; but as this latter takes an
oblique course backwards to its insertion into the mastoid process,
while the main blood-vessel dividing into branches still ascends in its
original direction, so is it that the artery becomes uncovered by the
muscle. Even the root of the internal carotid, E, may be readily reached
at this place, where it lies on the same plane as the external carotid,
but concealed in great part by the internal jugular vein. It would be
possible, while relaxing the sterno-mastoid muscle, to compress either
the common carotid artery or its main branches against the cervical
vertebral column, if pressure were made in a direction backwards and
inwards. The facial artery V, which springs from the external carotid,
D, may be compressed against the horizontal ramus of the lower jaw-bone
at the anterior border of the masseter muscle. The temporal artery, as
it ascends over the root of the zygoma, may be compressed effectually
against this bony point.
The external jugular vein, H, Plate 4, as it descends the neck from the
angle of the jaw obliquely backwards over the sterno-mastoid muscle, may
be easily compressed and opened in any part of its course. This vein
courses downwards upon the neck in relation to that branch of the
superficial cervical plexus, named auricularis magnus nerve, Q, Plate 4,
G, Plate 3. The nerve is generally situated behind the vein, to which it
lies sometimes in close proximity, and is liable, therefore, to be
accidentally injured in the performance of phlebotomy upon the external
jugular vein. The coats of the external jugular vein, E, Plate 3, are
said to hold connexion with some of the fibres of the platysma-myoides
muscle, A A, Plate 3, and that therefore, if the vessel be divided
transversely, the two orifices will remain patent for a time.
The position of the carotid artery protects the vessel, in some degree,
against the suicidal act, as generally attempted. The depth of the
incision necessary to reach the main blood-vessels from the fore part of
the neck is so considerable that the wound seldom effects more than the
opening of some part of the larynx. The ossified condition of the
thyroid and cricoid parts of the laryngeal apparatus affords a
protection to the vessels. The more oblique the incision happens to be,
the greater probability is there that the wound is comparatively
superficial, owing to the circumstance of the instrument having
encountered one or more parts of the hyo-laryngeal range; but woeful
chance sometimes directs the weapon horizontally through that membranous
interval between the thyroid and hyoid pieces, in which case, as also in
that where the laryngeal pieces persist permanently cartilaginous, the
resistance to the cutting instrument is much less.
The anatomical position of the parotid, H, Plate 3, and submaxillary
glands, W, Plate 4, is so important, that their extirpation, while in a
state of disease, will almost unavoidably concern other principal
structures. Whether the diseased parotid gland itself or a lymphatic
body lying in connexion with it, be the subject of operation, it seldom
happens that the temporo-maxillary branch of the external carotid, F,
escapes the knife. But an accident, much more liable to occur, and one
which produces a great inconvenience afterwards to the subject, is that
of dividing the portio-dura nerve, S, Plate 4, at its exit from the
stylo-mastoid foramen, the consequence being that almost all the muscles
of facial expression become paralyzed. The masseter, L, Plate 3,
pterygoid, buccinator, 15, Plate 4, and the facial fibres of the
platysma muscles, A O, Plate 3, still, however, preserve their power, as
these structures are innervated from a different source. The orbicularis
oculi muscle, which is principally supplied by the portio-dura nerve, is
paralyzed, though it still retains a partial power of contraction, owing
to the anatomical fact that some terminal twigs of the third or motor
pair of nerves of the orbit branch into this muscle.
The facial artery, V, and the facial vein, U, Plate 4, are in close
connexion with the submaxillary gland. Oftentimes they traverse the
substance of it. The lingual nerve and artery lie in some part of their
course immediately beneath the gland. The former two are generally
divided when the gland is excised; the latter two are liable to be
wounded in the same operation.
DESCRIPTION OF PLATES 3 & 4.
PLATE 3.
A A A. Subcutaneous platysma myoides muscle, lying on the face, neck,
and upper part of chest, and covering the structures contained
in the two surgical triangles of the neck.
B. Lip of the thyroid cartilage.
C. Clavicular attachment of the trapezius muscle.
D. Some lymphatic bodies of the post triangle.
E. External jugular vein.