digital depressions found there on each bone,
are firmly implanted the inter-osseous ligaments,
composing the remainder of the articulation.
These consist of very strong and coarsely
interlacing fibres passing almost directly from
bone to bone, inclosing large meshes which
are filled with a soft loose synovial looking
fat, and containing many veins. Behind,
these are continued into the deep posterior
sacro-sciatic ligaments.

The superior sacro-iliac ligament (fig. 80. a)
is a strong layer of fibres passing from the
lateral masses of the sacral base to the pos-
terior edge of the internal iliac fossa. It is
continued in front to the anterior sacro-iliac



ligament (>), similar in character to the
last, but thinner and more feeble, passing
from the first three bones of the sacrum to
the superior border of the iliac notch. The
former of these assist to prevent downward
and backward displacement, and the latter
upward and backward displacement ; the
position of the former being more anterior
than superior, and the position of the latter
more inferior than anterior in the proper
position of the pelvis.

By far the most powerful of the ligaments of
this articulation, and that which must be con-
sidered as the chief means of supporting the
great downward pressure at this joint, are the
posterior sacro -iliac ligaments. These are di-
vided into deep and superficial layers of fibres.

The deep layer (fig. 89. page 144. e) passes
from a well-marked prominence on the anterior
surface of the iliac tuberosity, downwards and
inwards, to the superior lateral part of the pos-
terior surface of the sacrum, principally to the
two upper pieces, external to the foramina ; the
fibres spreading out in interlacing bundles to-
wards the broader surface of implantation on
the sacrum, becoming longer as they become
more superficial, and leaving meshes for the
interposition of masses of loose fat, and the
passage of numerous small veins. The erector
spinae muscles arise from the surface of this
ligament, and cover it. To obtain a good
view of these fibres, a transverse section along
the brim of the true pelvis should be carried
backward through the sacrum, as shown in
the figures. This will show the manner in
which the tuberosities of the ilium hang over
the sacrum, suspended, as it were, between
them by these ligaments. It will be more par-
ticularly explained when treating on the me-
chanics of the pelvis. The superficial posterior
sacro'iliac ligament (Jig. 8 1 ., next page, a) has
been termed oblique, from the direction of its
fibres ; or long, from the extent of them. It is
attached above to the posterior superior spine
of the ilium, and passes downwards and ob-
liquely a little inwards to be implanted jnto the
fourth transverse tubercle of the sacrum ex-
ternal to the hole. To the sides of this liga-
ment, which is almost subcutaneous, are at-
tached the fascia lumborum and great gluteus
muscle. This ligament is described by Cru-
veilhier to be attached to the third sacral
vertebra. In all the cases I have seen, it is
attached to the fourth transverse tubercle,
which is the most prominent tubercular pro-
jection in the dried bone. Bichat erroneously
calls it " sacro-spinous."

Attached to the same sacral tubercle, and
passing horizontally outwards to be im-
planted into the posterior surface of the in-
ferior posterior spine of the ilium, a point
exactly corresponding to the termination of
the horizontal limb of the sacro-iliac articular
surface, is another well-marked ligament
(fig. 81. b), which, being separated by a dis-
tinct cellular interval from the deep ligaments
and distinguished by the more deeply seated
position and horizontal direction of its fibres
from the oblique ligament (a), and from the



the name of the inferior or short^ superficial
posterior sacro-iliac Sgament. This ligament
has been hitherto apparently confounded with
the great sacro-sciatic, which is attached to
its lower border by a thin fibrous extension.

fts. 81.



124 PELVIS.

great sacro-sciatic ligament (r), I think merits pelvis postictnn magnum, fg. 81. c) is attached
- - ~ ' * - ~i behind, to the posterior inferior spine ot the

ilium by a membranous expansion (e); to the
superficial posterior sacro-iliac ligaments with
which its fibres are blended; to the posterior
surface and borders of the two last pieces of
the sacrum ; and to the posterior sacro- coccy-
gean ligament and borders of the two or three
upper coccygeal bones. From this broad at-
tachment its fibres pass downwards, forwards,
and outwards to be implanted into the whole
length of the raised inner border of the great
tuberosity of the ischium. The fibres of this
ligament are arranged in fasciculi, which cross
each other in an X-like manner, so as to
present, at the extremities, an expanded
appearance, and in the centre a thick con-
tracted rounded outline. The fibres which
are placed superiorly in one extremity of
insertion cross at the contracted part to
become inferior at the other extremity, while
those which are internal cross in the opposite
direction to become external. Its superior
border, consequently, is directed outwards
and forwards, and its inferior border inwards,
and both present a curvilinear outline. At its
insertion into the sciatic tuberosity, the fibres
of the lower border present a falciform margin
having the concavity directed upwards along
the inner edge of the tuberosity, where it is
united to the fascia covering the obturator in-
ternus muscle. Its superficial or external
fibres are continued over the tuberosity in-
feriorly into the tendons of the biceps flexor
cruris, and semi-tendinosus muscles. Near the
posterior extremity, this ligament is almost
invariably perforated by a small hole, through
which passes the coccygeal branch of the
ischiadic artery. To the whole length of its
external or posterior surface is attached the
great glutens muscle, which causes it when
dissected to be very rough and flocculent. At
the posterior half of its inner surface it is
blended intimately with the lesser sacro-sciatic
ligament, anterior to which it is smooth, and
forms part of the boundary of the ischio-
rectal fossa.

The lesser or internal sacro-sciatic ligament
(ligamentum pelvis posticum parvum, Jig. 81.
d) lies internal to the last, in common with
which it is attached posteriorly to the side of
the two last pieces of the sacrum and of the
two upper pieces of the coccyx. At its an-
terior extremity it is contracted into a pointed
insertion into the spine of the ischium. The
direction of this ligament is horizontally for-
wards and outwards, and its shape is triangular,
so that its anterior contracted portion diverges
from the great sacro-sciatic ligament, leaving
a triangular opening between them through
which pass the obturator muscle out of, am'
the pudic vessels and nerves into the pelvis
This ligament, thus passing from the sacrum
across to the ischium, converts the sacro-
sciatic notch into a triangular or oval foramen
through which pass the pyramidalis muscle,
the gluteal, ischiadic and pudic vessels, and the
superior gluteal and great and lesser sciatic
and pudic nerves out of the pelvis. With its




Posterior view of the ligaments of the pelvis.

a, oblique posterior sacro-iliac ligament ; b, infe-
rior posterior superficial sacro-iliac ligament; c,
great sacro-sciatic ligament ; d, lesser sacro-sciatic
ligament ; e, membranous expansion over the pyri-
formis muscle.

The ligaments which may be considered as
accessory to this articulation are three in
number the ilio-lumbar ligament above, and
the greater and lesser sacro-sciatic ligaments
below.

The ilio-lumbar ligament (fig. 80. c} is a
triangular fascicular ligament, thickest at
the edges, and passing from the tip of the
last lumbar transverse process, to which its
apex is attached, horizontally outwards, and a
little backwards to the posterior fifth of the
inner lip of the crest of the ilium, along which
its fibres spread as far forward as the inner
projecting point of the posterior curve. To
the outer side and behind this ligament is
attached the quadratus lumborum muscle
with the tendon of the transversalis abdo-
minis, and to its front the psoas magnus
muscle. Meckel describes this ligament as
sometimes reaching as high as the transverse
process of the fourth lumbar vertebra. He
also describes a second ligament lower than
the preceding, but arising from the iliac crest
a little behind it. They are called by him,
respectively, the upper and lower anterior
pelvic ligaments, the latter corresponding to
the sacro-vertebral ligament before described.
The great sacro-sciatic ligament (ligamentum



PELVIS.



125



anterior or internal surface are blended the
fibres of the ischio-coccygeus muscle, which
exclude it from the ischio-rectal fossa, and
render it rough when dissected.

Soemmering describes the lower part of the
powerful lumbar fascia as a ligament connect-
ing the ilia to each other posteriorly and to
the lower spines of the sacrum. This fascia
does, doubtless, act powerfully in clasping
the ilia upon the sacrum between them. He
calls it the lateral sacro-iliac ligament, or the
posterior lateral iliac ligament.

The important part which these three ac-
cessory ligaments play in the mechanism of
the pelvis will be hereafter shown.

The movements of the sacro-iliac joint are
very limited indeed, its principal characteristic
being compactness and strength, with just
sufficient sliding motion downwards and back-
wards to break the shock of concussion pass-
ing from the lower extremities to the trunk.
This is said by some to be increased in preg-
nancy and by parturition.

The pubic symphysis (fig. 80. 2) is an azygos
joint uniting the innominate bones by their
pubic portions in front. The osseous surfaces
composing it are oval, with the long diameter
directed downwards and backwards, and ge-
nerally an inch and a half long, by three
quarters broad. The planes of these sur-
faces not being directly opposed to each other,
leave a larger interval of separation in front
than behind. This interval is filled by a fibro-
cartilaginous disc, which is correspondingly
thicker in front, where the fibrous components
are so numerous and strong as to constitute
almost an interosseous ligament, and pass
from one bone to the other in an oblique and
concentric direction. Towards the central
and posterior part this disc is generally mainly
cartilaginous in structure, and is often, in
females, separated in the middle by a chink
forming two smooth, plane, oval contiguous
articular surfaces, of various dimensions, some-
times irregularly laminar, at others with a de-
licate investing membrane. In parturient wo-
men these surfaces often extend over nearly
the whole of the articulation, and are well
marked in a figure given by Dr. Hunter, in
the second volume of Medical Observations
and Inquiries. In males, this separation is
seldom present. The whole of the disc may,
however, by maceration, generally be separated
into two plates {fig. 82. a, a), of a denser and
more cartilaginous structure than the rest,
each strongly adherent to the bone by mammil-
liform fibrous processes (b), which pass into
corresponding depressions in the osseous sur-
faces (c), and are connected to each other on
opposite sides, by continuation of their fibres,
arranged in oblique and concentric layers,
which interlace obliquely with each other, (rf)
Dr. W. Hunter remarks, with Sandifort and
Albinos, that the two cartilaginous plates (a,ff),
covering the opposed surfaces of theossa pubis,
are usually connected by a structure rather liga-
mentous than cartilaginous ; and in a memoir
on the pubic symphysis, gives an engraving of
this arrangement. In several instances I have



seen the fibrous processes which connect the
plates with the bone very well marked, leav-

Ftg. 82.




Symphysis pubis after maceration.

a, cartilaginous plates of Dr. Hunter ; ft, mam-
millary processes on their osseous surface ; c, cor-
responding osseous depressions to receive them ; d,
inter-laminar concentric nbro-cartilaginous tissue
divided vertically in the centre.

ing on the bone, after maceration, deep conical
pits. The above figure was taken from a ma-
cerated preparation of this joint. According
to the observations of Tenon, these processes
are directed into the bone downward and
backward, as well as outward, and tend to
prevent displacement of the cartilage in that
direction. The inter-laminar fibro-cartuUigin-
ous tissue is very elastic and yielding, swelling
out on the cut surface when lateral pressure
is made on the bone, somewhat in the manner
of the intervertebral discs. It often evinces
a tendency to split in a lamellar direction after
maceration. Around the circumference the
concentric fibres become much more numerous
and strong, and are continued into the peri-
pheral ligaments. These are an anterior, pos-
terior, a superior, and an inferior ligament.

The anterior pubic ligament (fig. 80. rf) is a
thick layer, passing between the anterior sur-
faces of the bones, strengthened by and blended
with the oblique fibres of the aponeurosis of
the external oblique muscle continued to the
opposite pubic bone in front of the joint.

The posterior pubic ligament is the most feeble.
It is composed of transverse fibres, somewhat
scattered, and is remarkable in being raised by
the posterior border of the pubic fibro-car-
tilage into a vertical ridge, in old persons often
very evident to the touch. It gives attachment
to the superior true ligaments of the bladder,
and the anterior fibres of the levator ani
muscle.

The superior pubic ligament (e) is formed
by a thick, smooth layer of fibres often raised
by a central ridge like the posterior, passing
between the crests of the pubes, the super-
ficial fibres extending over the greater part of
the crests, and giving origin to the recti ab-
dominales and pyramidales abdominal muscles,
and lineaalba.



126



PELVIS.



The inferior or sub-pubic ligament, (Hga~
mentum arcuatum, f~) is the most powerful,
passing from one descending ramus of the
pubis to the other in an arched form. Its
place of attachment to the pubis is often
a well-marked surface, triangular, with the
base upward, and half an inch in depth, cor-
responding in this respect to the outline of the
section of this ligament. This ligament and
the anterior are the most intimately con-
nected with the fibro-cartilage of the joint.
It unites below with the two layers of the
deep perineal fascia or triangular ligament, be-
tween which it gives origin to the vertical
compressors urethra, and forms the superior
boundary of the pubic arch, the apex of which
it rounds off and smoothens.

The movements of the pubic symphysis are
confined to a slightly yielding sliding motion
giving elasticity to the resistance of the pelvic
ring.

The obturator or thyroid membrane (g) is a
fascial aponeurosis rather than a ligament,
which closes in the oval foramen of that name.
It is composed of layers of fibres, intermin-
gling in a circular direction, and generally
congregated more in some places than others.
These are attached to the rough narrow bor-
der of the descending branch of the ischium
externally, but at the internal half of its cir-
cumference it is attached to the posterior sur-
face of the ascending branch of the ischium
and descending branch of the pubis, overlap-
ping in this situation the borders of these
bones posteriorly. Superiorly, it is inter-
rupted by passing over from one edge of the
sub-pubic notch to the other, so as to form
the lower boundary of a foramen for the pas-
sage of the obturator nerves and vessels.
Opposite the cotyloid notch its fibres are
continued into the capsular ligament invest-
ing the hip joint. By its anterior surface, it
gives attachment to the obturator external
muscle, and, by its posterior surface, to the
internal muscle of the same name. It is some-
times deficient in one or more places.

GENERAL APPEARANCE OF THE ARTICU-
LATED PELVIS. When the bones of the
pelvis are articulated together, its whole ap-
pearance is that of a section of a cylinder
or bent tube, having an anterior, posterior, and
two lateral, and a superior and inferior aspects.

Its anterior aspect (fig. 80.) is bounded on
each side by a line passing from the anterior
superior iliac spine, along the anterior border
of the cotyloid cavity to the ischiadic tube-
rosity on each side. It presents the pubic
symphysis directed downwards and forwards
in the median line, and the obturator fora-
mina directed forwards, outwards, and down-
wards on each side. As first noticed by
Ouvier, this oblique direction of the sym-
phvsis pubis is peculiar to the human species,
that of animals being parallel with the axis
of the body. In addition to these parts,
already described, are two large notches
formed by the approximation of the inno-
minate bones. Of these the superior one,
which maybe called the ventral notch, is formed



by the vertical and horizontal portions of the
anterior border of the innominate bones on
each side with the peculiarities before men-
tioned in its description. In the natural posi-
tion of the pelvis this notch exposes to the
view most of the internal surfaces of the pelvis
to be described from the superior aspect. The
inferior notch is formed by the oblique ascent
towards the symphysis pubis of the branches
of the ischium and pubis, forming what is
termed the sub-pubic arch. Its apex is limited
by the arched sub-pubic ligament, and there,
in the male, it is generally about an inch
wide, and at the base, between the ischiadic
tuberosities, about three inches wide. The
edges of this arch are in both sexes projected
forwards, more or less, so as to present an in-
clined surface to the plane of the arch. This
eversion as well as the measurements are,
however, considerably greater in the female
pelvis, hereafter to be considered.

The lateral aspects of the pelvis present
the anterior half of the external surface of
the ilia above ; the cotyloid cavities directed
outwards, -forward and downwards, in the
middle ; and the descending branch and
hinder part of the tuberosity of the ischia
below, the latter being directed outwards
and backwards.

The posterior aspect presents the posterior
surface of the sacrum and coccyx in the cen-
tre, the most prominent point, in the erect
position of the body, being the divided spine
of the fourth sacral vertebra. On each side,
next in succession, occur the overhanging and
projecting tuberosities of the ilia, constituting
two prominences next in importance, conceal-
ing the sacro-iliac articulations, and caus-
ing the lateral parts of the three upper
sacral bones to appear as a deep groove on
each side for the reception and origin of the
powerful erector muscles of the back. Be-
tween these points also the last lumbar ver-
tebra appears sunk between the two iliac crests,
so that its upper surface is on a level with
their most elevated central portion. Below
the sacrum, the coccyx projects downwards
and forwards in a salient median point, which
separates and completes the inner boundary
of the sciatic notches on each side, converted
into foramina by the greater and lesser sacro-
sciatic ligaments. The distance of the edges
of the sacrum and coccyx from the spines and
tuberosities of the ischia, and consequently
the size of the openings, is less in the male than
in the female ; but the depth of the notches
vertically is greater in the former. Above these
are seen the posterior half of the external iliac
surface, or external iliac fossa, surmounted by
the rising crest.

The superior aspect (fig. 80.) reveals to view
the whole of the internal surface of the pelvis,
which presents two well contrasted portions,
divided by a rounded edge or border, of which
the superior is wide, expanded, and deficient
in front, and is called the large, or false pelvis ;
and the inferior, narrower, more complete, and
more compact, is called the small, or true
pelvis; while the border which separates them



PELVIS.



127



is commonly expressed as the brim, or su-
perior outlet of the true pelvis.

The false pelvis is formed laterally by the con-
cave surface of the internal iliac fossae directed
upwards, forwards, and inwards ; and poste-
riorly by the lateral masses of the base of the
sacrum, directed upwards and forwards. In the
middle is also seen, in the articulated pelvis,
the anterior surface of the body of the last
lumbar vertebra, filling up, with the pelvi-
lumbar ligaments, the notch otherwise left be-
tween the ilia behind. The superior border
of the false pelvis is formed by the ilio-lumbar
ligaments (\\ hich exclude the iliac tuberosities),
and the anterior three- fourths of the iliac
crest, the most prominent point of which, in
the proper position of the pelvis, is the centre
of the posterior curve. It is terminated sud-
denly, in front, by the anterior superior iliac
spine, where the ventral notch commences: by
the deficiency of osseous structure at this
part.

The brim of the pelvis is a heart-shaped
opening, formed posteriorly by the body of
the first sacral vertebra which overhangs the
cavity of the true pelvis, so as to form a pro-
jection called the promontory of the sacrum (i),
corresponding to the indentation in the emble-
matical heart-shape. On each side of this, the
rounded arched anterior borders of the lateral
masses of the sacral base continue the brim
across the sacro-iliac joint, to the thick rounded
ridge on the inner surface of the ilium, which
is prolonged behind the ilio-pectineal eminence
to the horizontal branch of the pubis where
the brim becomes identified with the pectineal
line. Finally, the brim is completed anteriorly
by the shelving border of the body of the pubis,
immediately behind the crest, and by the
rounded superior part of the pubic symphysis.
The part of the brim of the pelvis which is
formed by the two portions of the innominate
bone is sometimes called the linea ilio-pectinea,
or, by some, the linea innominata. Sometimes
the brim is called the inlet of the true pelvis.
The cavity of the true pelvis is formed
laterally by the plane sloping inner surfaces
of the lower part of the ilia, opposite the
cotyloid cavities, and of the descending
branches of the ischia, the latter being termed
by obstetricians the planes of the ischia ; in
front, by the posterior surfaces of the branches
and symphysis of the pubis, and by the as-
cending branches of the ilia ; and behind, by
the whole concave anterior surface of the
sacrum and coccyx, the former being some-
times called the hollow of the sacrum. From
the oblique position of the pelvis, the posterior
wall, which is the deepest, also reaches the
highest, and the lateral walls the lowest ; the
sub-pubic arch cutting out the anterior wall
and leaving only the short symph\sis pubis to
represent it. The interval between the sa-
crum and ossa innominata behind, forming the
sacro-sciatic notch, is completed and bounded
by the sacro-sciatic ligaments, the inner sur-
faces of which are seen in this view. The
inner surface of the coccyx is also seen to
have an aspect directed upwards and for-



wards, and the spines of the ischia to project
considerably inwards, so as to present two
opposite points, the distance between which
may sometimes be of great importance in
parturition. This projection is much greater
in the male than the female> and will be al-
luded to in the relative measurements of the
pelvis. The cavity of the pelvis contracts
uniformly downwards at the sides by reason
of the inclination of the innominate bones ;
but, from the vertical curvature of the sacrum,
the antero-posterior diameter is much greater
in the middle than at the superior or inferior
outlets, which are hence termed straits. The
presence of the obturator foramina antero-
laterally, and of the sacro-sciatic foramina
postero-laterally, must also be remarked as
constituting four openings, diagonally op-
posed to each other, capable, from the yield-
ing nature of the structures filling them, of
enlarging these diameters under sufficient
pressure The great projection, forwards, of
the coccyx and lower end of the sacrum may
be considered as compensated for by the de-
ficiency of the anterior wall in the sub-pubic
arch directly opposite to them, gradually
widening downwards as they advance. Both
the forward direction of the coccyx, and the
width of the pubic arch, are peculiar to the