liability to fracture. Its rounded shape diffuses, as is the case with
all rotund forms, the force which happens to strike upon it. The mode in
which the cranium is set upon the cervical spine serves also to diffuse
the pressure at the points where the two opposing forces meet--viz., at
the first cervical vertebra E and the cranial basilar process F. This
fact might be proved upon mechanical principle.
The tegumentary envelope of the head, as well as the dura-matral lining,
serves to damp cranial vibration consequent upon concussion; while the
sutural isolation of the several component bones of the cranium also
prevents, in some degree, the extension of fractures and the vibrations
of concussion. The contents of the head, like the contents of all hollow
forms, receive the vibratory influence of force externally applied. The
brain receives the concussion of the force applied to its osseous
envelope; and when this latter happens to be fractured, the danger to
life is not in proportion to the extent of the fracture here, any more
than elsewhere in the skeleton fabric, but is solely in proportion to
the amount of shock or injury sustained by the nervous centre.
When it is required to trephine any part of the cranial envelope, the
points which should be avoided, as being in the neighbourhood of
important bloodvessels, are the following--the occipital protuberance,
B, within which the "torcular Herophili" is situated, and from this
point passing through the median line of the vertex forwards to Z the
frontal sinus, the trephine should not be applied, as this line marks
the locality of the superior longitudinal sinus. The great lateral sinus
is marked by the superior occipital ridge passing from the point B
outwards to the mastoid process. The central point B of the side of the
head, Plate 21, marks the locality of the root of the meningeal artery
within the cranium, and from this point the vessel branches forwards and
backwards over the interior of the cranium.
The nasal fossae are situated on either side of the median partition
formed by the vomer and cartilaginous nasal septum. Both nasal fossae
are open anteriorly and posteriorly; but laterally they do not, in the
normal state of these parts, communicate. The two posterior nares
answering to the two nasal fossae open into the upper part of the bag of
the pharynx at 8, Plate 20, which marks the opening of the Eustachian
tube.
The structures observable in both the nasal fossae absolutely
correspond, and the foramina which open into each correspond likewise.
All structures situated on either side of the median line are similar.
And the structure which occupies the median line is itself double, or
duality fused into symmetrical unity. The osseous nasal septum is
composed of two laminae laid side by side. The spongy bones, X W, are
attached to the outer wall of the nasal fossa, and are situated one
above the other. These bones are three in number, the uppermost is the
smallest. The outer wall of each naris is grooved by three fossae,
called meatuses, and these are situated between the spongy bones. Each
meatus receives one or more openings of various canals and cavities of
the facial apparatus. The sphenoidal sinus near F opens into the upper
meatus. The frontal, Z, and maxillary sinuses open into the middle
meatus, and the nasal duct opens into the inferior sinus beneath the
anterior inferior angle of the lower spongy bone, W.
In the living body the very vascular fleshy and glandular Schneiderian
membrane which lines all parts of the nasal fossa almost completely
fills this cavity. When polypi or other growths occupy the nasal fossae,
they must gain room at the expense of neighbouring parts. The nasal duct
may have a bent probe introduced into it by passing the instrument along
the outer side of the floor of the nasal fossa as far back as the
anterior inferior angle of the lower spongy bone, W, at which locality
the duct opens. An instrument of sufficient length, when introduced into
the nostrils in the same direction, will, if passed backwards through
the posterior nares, reach the opening of the Eustachian tube, 8.
While the jaws are closed, the tongue, R, Plate 20, occupies the oral
cavity almost completely. When the jaws are opened they form a cavity
between them equal in capacity to the degree at which they are sundered
from each other. The back of the pharynx can be seen when the jaws are
widely opened if the tongue be depressed, as R, Plate 20. The hard
palate, U, which forms the roof of the mouth, is extended further
backwards by the soft palate, V, which hangs as the loose velum of the
throat between the nasal fossae above and the fauces below. Between the
velum palati, V, and the root of the tongue, we may readily discern,
when the jaws are open, two ridges of arching form, 5, 6, on either side
of the fauces. These prominent arches and their fellows are named the
pillars of the fauces. The anterior pillar, 5, is formed by the
submucous palato-glossus muscle; the posterior pillar, 6, is formed by
the palato-pharyngeus muscle. Between these pillars, 5 and 6, is
situated the tonsil, S, beneath the mucous membrane. When the tonsils of
opposite sides become inflamed and suppurate, an incision may be made
into either gland without much chance of wounding the internal carotid
artery; for, in fact, this vessel lies somewhat removed from it behind.
In Plate 21, that point of the superior constrictor of the pharynx,
marked D, indicates the situation of the tonsil gland; and a
considerable interval will be seen to exist between D and the internal
carotid vessel F.
If the head be thrown backwards the nasal and oral cavities will look
almost vertically towards the pharyngeal pouch. When the juggler is
about to "swallow the sword," he throws the head back so as to bring the
mouth and fauces in a straight line with the pharynx and oesophagus. And
when the surgeon passes the probang or other instruments into the
oesophagus, he finds it necessary to give the head of the person on whom
he operates the same inclination backwards. When instruments are being
passed into the oesophagus through the nasal fossa, they are not so
likely to encounter the rima glottidis below the epiglottis, 9, as when
they are being passed into the oesophagus by the mouth. The glottis may
be always avoided by keeping the point of the instrument pressing
against the back of the pharynx during its passage downwards.
When in suspended animation we endeavour to inflate the lungs through
the nose or mouth, we should press the larynx, 10, 11,12, backwards
against the vertebral column, so as to close the oesophageal tube.
DESCRIPTION OF PLATES 20 & 21.
PLATE 20.
A A. The dura-matral falx; A*, its attachment to the tentorium.
B. Torcular Herophili.
C. Dura-mater lining the spinal canal.
D D*. Axis vertebra.
E E*. Atlas vertebra.
F F*. Basilar processes of the sphenoid and occipital bones.
G. Petrous part of the temporal bone.
H. Cerebellar fossa.
I I*. Seventh cervical vertebra.
K K*. First rib surrounding the upper part of the pleural sac.
L L*. Subclavian artery of the right side overlying the pleural sac.
M M*. Right subclavian vein.
N. Right common carotid artery cut at its origin.
O. Trachea.
P. Thyroid body.
Q. Oesophagus.
R. Genio-hyo-glossus muscle.
S. Left tonsil beneath the mucous membrane.
T. Section of the lower maxilla.
U. Section of the upper maxilla.
V. Velum palati in section.
W. Inferior spongy bone.
X. Middle spongy bone.
Y. Crista galli of oethmoid bone.
Z. Frontal sinus.
2. Anterior cartilaginous part of nasal septum.
3. Nasal bone.
4. Last molar tooth of the left side of lower jaw.
5. Anterior pillar of the fauces.
6. Posterior pillar of the fauces.
7. Genio-hyoid muscle.
8. Opening of Eustachian tube.
9. Epiglottis.
10. Hyoid bone.
11. Thyroid bone.
12. Cricoid bone.
13. Thyroid axis.
14. Part of anterior scalenus muscle.
15. Humeral end of the clavicle.
16. Part of posterior scalenus muscle.
[Illustration: Head and neck, in section, from front to back; showing
blood vessels, muscles and other internal organs.]
Plate 20
PLATE 21.
A. Zygoma.
B. Articular glenoid fossa of temporal bone.
C. External pterygoid process lying on the levator and tensor palati
muscles.
D. Superior constrictor of pharynx.
E. Transverse process of the Atlas.
F. Internal carotid artery. Above the point F, is seen the
glosso-pharyngeal nerve; below F, is seen the hypoglossal nerve.
G. Middle constrictor of pharynx.
H. Internal jugular vein.
I. Common carotid cut across.
K. Rectus capitis major muscle.
L. Inferior constrictor of pharynx.
M. Levator anguli scapulae muscle.
N. Posterior scalenus muscle.
O. Anterior scalenus muscle.
P. Brachial plexus of nerves.
Q. Trachea.
R R*. Subclavian artery.
S. End of internal jugular vein.
T. Bracheo-cephalic artery.
U U*. Roots of common carotid arteries.
V. Thyroid body.
W. Thyroid cartilage.
X. Hyoid bone.
Y. Hyo-glossus muscle.
Z. Upper maxillary bone.
2. Inferior maxillary branch of fifth cerebral nerve.
3. Digastric muscle cut.
4. Styloid process.
5. External carotid artery.
6 6. Lingual artery.
7. Roots of cervical plexus of nerves.
8. Thyroid axis; 8*, thyroid artery, between which and Q, the trachea,
is seen the inferior laryngeal nerve.
9. Omo-hyoid muscle cut.
10. Sternal end of clavicle.
11. Upper rings of trachea, which may with most safety be divided in
tracheotomy.
12. Cricoid cartilage.
13. Crico-thyroid interval where laryngotomy is performed.
14. Genio-hyoid muscle.
15. Section of lower maxilla.
16. Parotid duct.
17. Lingual attachment of styloglossus muscle, with part of the
gustatory nerve seen above it.
[Illustration: Head and neck, showing blood vessels, muscles and other
internal organs.]
Plate 21
COMMENTARY ON PLATE 22.
THE RELATIVE POSITION OF THE SUPERFICIAL ORGANS OF THE THORAX AND ABDOMEN.
In the osseous skeleton, the thorax and abdomen constitute a common
compartment. We cannot, while we contemplate this skeleton, isolate the
one region from the other by fact or fancy. The only difference which I
can discover between the regions called thorax and abdomen, in the
osseous skeleton, (considering this body morphologically,) results,
simply, from the circumstance that the ribs, which enclose thoracic
space, have no osseous counterparts in the abdomen enclosing abdominal
space, and this difference is merely histological. In man and the
mammalia the costal arches hold relation with the pulmonary organs, and
these costae fail at that region where the ventral organs are located.
In birds, and many reptiles, the costal arches enclose the common
thoracico-abdominal region, as if it were a common pulmonary region. In
fishes the costal arches enclose the thoracico-abdominal region, just as
if it were a common abdominal region. I merely mention these general
facts to show that costal enclosure does not actually serve to isolate
the thorax from the abdomen in the lower classes of animals; and on
turning to the human form, I find that this line of separation between
the two compartments is so very indefinite, that, as pathologists, we
are very liable to err in our diagnosis between the diseased and the
healthy organs of either region, as they lie in relation with the
moveable diaphragm or septum in the living body. The contents of the
whole trunk of the body from the top of the sternum to the perineum are
influenced by the respiratory motions; and it is most true that the
diaphragmatic line, H F H*, is alternately occupied by those organs
situated immediately above and below it during the performance of these
motions, even in health.
The organs of the thoracic region hold a certain relation to each other
and to the thoracic walls. The organs of the abdomen hold likewise a
certain relation to each other and to the abdominal parietes. The organs
of both the thorax and the abdomen have a certain relation to each
other, as they lie above and below the diaphragm. In dead nature these
relations are fixed and readily ascertainable, but in living, moving
nature, the organs influence this relative position, not only of each
other, but also of that which they bear to the cavities in which they
are contained. This change of place among the organs occurs in the
normal or healthy state of the living body, and, doubtless, raises some
difficulty in the way of our ascertaining, with mathematical precision,
the actual state of the parts which we question, by the physical signs
of percussion and auscultation. In disease this change of place among
these organs is increased, and the difficulty of making a correct
diagnosis is increased also in the same ratio. For when an emphysematous
lung shall fully occupy the right thoracic side from B to L, then G, the
liver, will protrude considerably into the abdomen beneath the right
asternal ribs, and yet will not be therefore proof positive that the
liver is diseased and abnormally enlarged. Whereas, on the other hand,
when G, the liver, is actually diseased, it may occupy a situation in
the right side as high as the fifth or sixth ribs, pushing the right
lung upwards as high as that level; and, therefore, while percussion
elicits a dull sound over this place thus occupied, such sound will not
be owing to a hepatized lung, but to the absence of the lung caused by
the presence of the liver.
In the healthy adult male body, Plate 22, the two lungs, D D*, whilst in
their ordinary expanded state, may be said to range over all that region
of the trunk of the body which is marked by the sternal and asternal
ribs. The heart, E, occupies the thoracic centre, and part of the left
thoracic side. The heart is almost completely enveloped in the two
lungs. The only portion of the heart and pericardium, which appears
uncovered by the lung on opening the thorax, is the base of the right
ventricle, E, situated immediately behind the lower end of the sternum,
where this bone is joined by the cartilages of the sixth and seventh
ribs. The lungs range perpendicularly from points an inch above B, the
first rib, downwards to L, the tenth rib, and obliquely downwards and
backwards to the vertebral ends of the last ribs. This space varies in
capacity, according to the degree in which the lungs are expanded within
it. The increase in thoracic space is attained, laterally, by the
expansion of the ribs, C I; and vertically, by the descent of the
diaphragm, H, which forces downwards the mass of abdominal viscera. The
contraction of thoracic space is caused by the approximation of all the
ribs on each side to each other; and by the ascent of the diaphragm. The
expansion of the lungs around the heart would compress this organ, were
it not that the costal sides yield laterally while the diaphragm itself
descends. The heart follows the ascent and descent of the diaphragm,
both in ordinary and forced respiration.
But however much the lungs vary in capacity, or the heart as to position
in the respiratory motions, still the lungs are always closely applied
to the thoracic walls. Between the pleura costalis and pulmonalis there
occurs no interval in health. The thoracic parietes expand and contract
to a certain degree; and to that same degree, and no further, do the
lungs within the thorax expand and contract. By no effort of expiration
can the animal expel all the air completely from its lungs, since by no
effort of its own, can it contract thoracic space beyond the natural
limit. On the other hand, the utmost degree of expansion of which the
lungs are capable, exactly equals that degree in which the thoracic
walls are dilatable by the muscular effort; and, therefore, between the
extremes of inspiration and expiration, the lungs still hold closely
applied to the costal parietes. The air within the lungs is separated
from the air external to the thorax, by the thoracic parietes. The air
within and external to the lungs communicate at the open glottis. When
the glottis closes and cuts off the communication, the respiratory act
ceases--the lungs become immovable, and the thoracic walls are (so far
as the motions of respiration are concerned) rendered immovable also.
The muscles of respiration cannot, therefore, produce a vacuum between
the pulmonic and costal pleura, either while the external air has or has
not access to the lungs. Upon this fact the mechanism of respiration
mainly depends; and we may see a still further proof of this in the
circumstance that, when the thoracic parietes are pierced, so as to let
the external air into the cavity of the pleura, the lung collapses and
the thoracic side ceases to exert an expansile influence over the lung.
When in cases of fracture of the rib the lung is wounded, and the air of
the lung enters the pleura, the same effect is produced as when the
external air was admitted through an opening in the side.
When serous or purulent effusion takes place within the cavity of the
pleura, the capacity of the lung becomes lessened according to the
quantity of the effusion. It is more reasonable to expect that the soft
tissue of the lung should yield to the quantity of fluid within the
pleural cavity, than that the rigid costal walls should give way
outwardly; and, therefore, it seldom happens that the practitioner can
discover by the eye any strongly-marked difference between the thoracic
walls externally, even when a considerable quantity of either serum,
pus, or air, occupies the pleural sacs.
In the healthy state of the thoracic organs, a sound characteristic of
the presence of the lung adjacent to the walls of the thorax may be
elicited by percussion, or heard during the respiratory act through the
stethoscope, over all that costal space ranging anteriorly between B,
the first rib, and I K, the eight and ninth ribs. The respiratory murmur
can be heard below the level of these ribs posteriorly, for the lung
descends behind the arching diaphragm as far as the eleventh rib.
When fluid is effused into the pleural cavity, the ribs are not moved by
the intercostal muscles opposite the place occupied by the fluid, for
this has separated the lung from the ribs. The fluid has compressed the
lung; and in the same ratio as the lung is prevented from expanding, the
ribs become less moveable. The presence of fluid in the pleural sac is
discoverable by dulness on percussion, and, as might be expected, by the
absence of the respiratory murmur at that locality which the fluid
occupies. Fluid, when effused into the pleural sac, will of course
gravitate; and its position will vary according to the position of the
patient. The sitting or standing posture will therefore suit best for
the examination of the thorax in reference to the presence of fluid.
Though the lungs are closely applied to the costal sides at all times in
the healthy state of these organs, still they slide freely within the
thorax during the respiratory motions--forwards and backwards--over the
serous pericardium, E, and upwards and downwards along the pleura
costalis. The length of the adhesions which supervene upon pleuritis
gives evidence of the extent of these motions. When the lung becomes in
part solidified and impervious to the inspired air, the motions of the
thoracic parietes opposite to the part are impeded. Between a solidified
lung and one which happens to be compressed by effused fluid it requires
no small experience to distinguish a difference, either by percussion or
the use of the stethoscope. It is great experience alone that can
diagnose hydro-pericardium from hypertrophy of the substance of the
heart by either of these means.
The thoracic viscera gravitate according to the position of the body.
The heart in its pericardial envelope sways to either side of the
sternal median line according as the body lies on this or that side. The
two lungs must, therefore, be alternately affected as to their capacity
according as the heart occupies space on either side of the thorax. In
expiration, the heart, E, is more uncovered by the shelving edges of the
lungs than in inspiration. In pneumothorax of either of the pleural sacs
the air compresses the lung, pushes the heart from its normal position,
and the space which the air occupies in the pleura yields a clear hollow
sound on percussion, whilst, by the ear or stethoscope applied to a
corresponding part of the thoracic walls, we discover the absence of the
respiratory murmur.
The transverse diameter of the thoracic cavity varies at different
levels from above downwards. The diameter which the two first ribs, B
B*, measure, is the least. That which is measured by the two eighth
ribs, I I*, is the greatest. The perpendicular depth of the thorax,
measured anteriorly, ranges from A, the top of the sternum, to F, the
xyphoid cartilage. Posteriorly, the perpendicular range of the thoracic
cavity measures from the spinous process of the seventh cervical
vertebra above, to the last dorsal spinous process below. In full,
deep-drawn inspiration in the healthy adult, the ear applied to the
thoracic walls discovers the respiratory murmur over all the space
included within the above mentioned bounds. After extreme expiration, if
the thoracic walls be percussed, this capacity will be found much
diminished; and the extreme limits of the thoracic space, which during
full inspiration yielded a clear sound, indicative of the presence of
the lung, will now, on percussion, manifest a dull sound, in consequence
of the absence of the lung, which has receded from the place previously
occupied.
Owing to the conical form of the thoracic space, the apex of which is
measured by the first ribs, B B*, and the basis by I I*, it will be seen
that if percussion be made directly from before, backwards, over the
pectoral masses, R R*, the pulmonic resonance will not be elicited. When
we raise the arms from the side and percuss the thorax between the folds
of the axillae, where the serratus magnus muscle alone intervenes
between the ribs and the skin, the pulmonic sound will answer clearly.
At the hypochondriac angles formed between the points F, L, N, on either
side the lungs are absent both in inspiration and expiration.
Percussion, when made over the surface of the angle of the right side,
discovers the presence of the liver, G G*. When made over the median
line, and on either side of it above the umbilicus, N, we ascertain the
presence of the stomach, M M*. In the left hypochondriac angle, the
stomach may also be found to occupy this place wholly.
Beneath the umbilicus, N, and on either side of it as far outwards as
the lower asternal ribs, K L, thus ranging the abdominal parietes
transversely, percussion discovers the transverse colon, O, P, O*. The
small intestines, S S*, covered by the omentum, P*, occupy the
hypogastric and iliac regions.
The organs situated within the thorax give evidence that they are
developed in accordance to the law of symmetry. The lungs form a pair,
one placed on either side of the median line. The heart is a double
organ, formed of the right and left heart. The right lung differs from
the left, inasmuch as we find the former divided into three lobes, while
the latter has only two. That place which the heart now occupies in the
left thoracic side is the place where the third or middle lobe of the
left lung is wanting. In the abdomen we find that most of its organs are
single. The liver, stomach, spleen, colon, and small intestine form a
series of single organs: each of these may be cleft symmetrically. The
kidneys are a pair.
The extent to which the ribs are bared in the figure Plate 22, marks
exactly the form and transverse capacity of the thoracic walls. The
diaphragm, H H*, has had a portion of its forepart cut off, to show how
it separates the thin edges of both lungs above from the liver, G, and
the stomach, M, below. These latter organs, although occupying abdominal
space, rise to a considerable height behind K L, the asternal ribs, a
fact which should be borne in mind when percussing the walls of the
thorax and abdomen at this region.
DESCRIPTION OF PLATE 22.
A. Upper bone of the sternum.
B B*. Two first ribs.
C C*. Second pair of ribs.
D D*. Right and left lungs.