from the additional number of its visceral
contents.
PELVIS.
137
According to Dupuytren, the female
pelvis differs very little' from that of the
male till puberty, at which period it has a
general triangular form in both sexes, but,
after that period, it becomes rapidly developed,
and soon assumes its distinctive sexual cha-
racter. The transverse diameters begin to
exceed the conjugate, and, in the female,
attain a great preponderance, constituting
one of the great characteristics of the fully
formed human pelvis, as distinguished from
that of the lower animals.
In Autenrieth's method of calculating the
pelvic dimensions, the dorsal, or posterior
part, bears a proportion to the anterior or
abdominal part, as 10 to from 11 to 14*, in
the infant of t\vo years ; while, in the adult
pelvis, it was as 10 to from 16 to 22.
In advanced adult age, the pelvic inclination
is said by Cruveilhier to be increased in con-
sequence of the forward curvature, or droop-
ing of the spinal column, which tends to
arrive at the horizontal position, as in quadru-
peds. To keep the centre of gravity between
the lower .extremities, the femurs, in old
persons, are more flexed upon the pelvis, so
as to be more directed towards the line of
the superior pelvic plane. 1 have found,
however, that in old subjects, although the
angle of the pelvic plane with that of the whole
spinal column is increased, yet the angle with
the lumbar vertebrae only, is not so much
changed, and that, apparently, the increased
muscular traction on the sacrum and posterior
part of the ilia by the muscles of the back act-
ing upwards, and of those of the front of the
thigh acting downwards, upon the anterior
part of the pelvic lever, in order to pre-
serve the erect position, produce this in-
creased obliquity of the pelvis, which is ge-
nerally accompanied by a corresponding de-
crease of the sacro-vertebral angle. This will
be more fully comprehended when consider-
ing the mechanism of the pelvis.
MUSCULAR ATTACHMENTS OF THE PEL-
VIS. To afford a fixed point for the attach-
ment of the numerous and powerful muscles
acting on the trunk and extremities is one of
the important offices of the pelvis. These
may be classed as posterior spinal and abdo~
minal groups acting on the trunk and spinal
column ; extensor, flexor, adductor, abductor,
and rotator groups acting on the lower extre-
mity ; and perineal grou])s forming the move-
able floor of the pelvis and acting on the
genital and excretory organs.
1 . ^Muscles acting on the trunk and spine.
The posterior spinal group. The longissimus
dorsi and multijidus spints, to the upper part
of the posterior surface of the sacrum ; the
interspma/es, to the superior border of the
sacral crest; and, according to some, the ex-
tensor coccygis, to the contiguous posterior
surfaces of the sacrum and coccyx ; the sacro-
lumbalis, to the middle part of the posterior
third of the iliac crest, and to the contiguous
sacral surface ; and the laHsshnus dorsi, through
the lumbar fascia to the external lip of the
posterior half of the iliac crest and to the
sacral crest. This muscle acts on the arm.
The abdominal group. The obliquus exter-
nus and internus, and transversalis abdo-
minis, to the external lip, middle ridge, and
internal lips respectively of the iliac crest, and
also by their aponeurotic tendons to the angle,
crest, spine, and pectineal line of the pubis
(the external oblique tendon, under the name
of Poupart's ligament, stretching across, from
the anterior superior iliac spine to the spine
of the pubis, and, under the name of Gim-
bernat's ligament, passing backwards to the
linea-ilio pectinea; and the internal oblique
and transversalis tendons enclosing the rectus
abdominis muscle, and uniting to form the
conjoined tendon) ; the quadratus lumborum,
to the posterior fourth of the inner lip of the
iliac crest ; the rectus and pyramidalis abdo-
miius, to the crest of the pubis; and the
psoas parvus, when present, to the pectineal
eminence.
2. Muscles acting on the leg. The flexor
group. The rectus femoris, to the anterior in-
ferior iliac spine and outer part of the coty-
loid rim; the iliacus, to the whole anterior
concave surface of the iliac wing the psoas
magnus is not attached to the pelvis, but acts
upon it by passing over it along the pelvic
brim ; and the sartorius, to the anterior supe-
rior iliac spine and notch below it.
The extensor group. The biceps flexor
cntris, semitendinosus, and semimembranosus,
to the depending middle and posterior parts
of the ischial tuberosity ; and the gluteus
maxiinus, to the quadrilateral gluteal impres-
sion on the dorsum of the ilium, to the pos-
terior surfaces of the two lower pieces of the
sacrum, and of the two or three upper pieces
of the coccyx, to the oblique sacro-iliac and
great sacro-sciatic ligaments, and to the lum-
bar fascia.
The adductor group. The adductor magnus,
to the anterior part of the ischial tuberosity,
and to the united ischio-pubic rami ; the ad-
ductor longus, to the anterior surface of the
angle of the pubis ; the adductor brevis below
the foregoing, to the same surface ; the pec-
tineus, to the spine, pectineal line, and hori-
zontal ramus of the pubis ; and the gracilis t
to the rough internal border of the ischio-
pubic rami and symphysis pubis.
The abductor grouji. The gluteus medius,
to the dorsum of the ilium, between the crest
and superior curved line ; the gluteus minimus,
to the same surface between the curved lines ;
and the tensor vaginte femoris, to the outer
surface of the anterior superior iliac spine.
The rotator groitp. The pyriforrnis, to the
anterior surface of the sacrum between the
four upper sacral holes, and passing out
through the great sciatic notch ; the obturator
externus, to the inner half of the external cir-
cumference of the obturator foramen, and to
the external surface of the membrane closing it;
the obturator internus, to the internal surface
of the same ligament, and to the borders of the
foramen, and also to the surface of bone oppo-
site the cotyloid cavity (this muscle passes out
through the small sciatic notch, over which
133
PELVIS.
it is bent as over a pulley) ; the gemcllus su-
perior, to the outer surface of the ischiadic
spine; the gemellus inferior, to the posterior
extremity of the ischiadic tuberosity ; and the
quadratus femoris, to the external border of
the same tuberosity.
3. Muscles acting on the perineum and ge-
nitals. The posterior perineal group. The
levator ani, to the middle of the inner surface
of the symphysis pubis, to the inner surface
of the ischiadic spine, and to the tip of the
coccyx; the ischio-coccygeus, to the same inner
surface of the ischiadic spine, to the lateral
border of the coccyx, and to the inner surface
of the small sacro-sciatic ligament ; and the
sphincter ani, to the tip of the coccyx.
The anterior perineal group. The trans-
versus perinei, to the middle of the inner
border of the ischial tuberosity; the accelerator
urinfB (or, in the female, the sphincter vagince),
to the anterior part of the inner border of the
ischial tuberosity ; the erector penis (or, in the
female, clitoridis), to the ascending ramus of
the ischium ; and the compressors urethra;,
to the descending ramus of the pubis, and to
the sub-pubic ligament.
FASCIAL ATTACHMENTS. Besides the fore-
going, the pelvis also affords attachment to
many important fascics, which are susceptible
of division into lumbar, abdominal, crural,
pelvic, and perineal.
The lumbar fascia is formed by the junction
of the tendon of the latissimus dorsi muscle
with the fascia vertebralis, and the united
posterior tendons of the internal oblique and
external division of the transversalis tendon,
and it is attached along the sacral crest and
posterior surface of the fourth sacral bone,
and to the posterior half of the iliac crest,
enclosing the sacro-lumbalis muscle.
The abdominal fascia; are three in number,
viz., the fascice transversalis, attached along
the inner lip of the iliac crest, to Poupart's
ligament, and to the crest, spine, and pec-
tineal line of the pubis ; the fascia of the qua-
dratus lumborum muscle, or anterior division of
the tendon of the transversalis, attached to
the inner lip of the posterior fourth of the
iliac crest, and to the ilio-lumbar ligament;
and the iliac fascia, attached to the ilio-lumbar
ligament, along the inner margin of the iliac
crest, and to the anterior superior iliac spine.
The crural fascia or fascia lata is divided into
three portions, named, from their respective
attachments to the three portions of the inno-
minate bone, iliac, pubic, and ischiadic. The
outer lip of the iliac crest, the anterior superior
spine, and Poupart's ligament, give attachment
to the iliac portion, which separates the lateral
abdominal from the external leg muscles ; the
spine, crest, angle, pectineal line, and descend-
ing ramus of the pubis, to the pubic portion,
which separates the internal leg muscles from
the anterior abdominal tmd anterior perineal
group of muscles ; and the tuberosity and
ascending ramus of the ischium to the ischiadic
portion, which separates the posterior leg
muscles from the posterior muscles of the
perineal group.
The pelvic fascia is composed of two por-
tions, the rccto-vesical and obturator, which,
having a common attachment to the anterior
surface and promontory of the sacrum, to the
anterior and lateral parts of the pelvic brim,
and to the iliac fascia, separate opposite the
line of origin of the levator ani muscle, which
arises between them, from the symphysis pubis
to the ischiadic spine. The obturator division
is attached to the inner margins of the ischiadic
tuberosity and ischio-pubic rami, being con-
nected with the falciform margin of the great
sacro-sciatic ligament behind, and secluding
the obturator muscle from the ischio-rectal
fossa ; the recto-vesical division, forming the
anterioi ind lateral true ligaments of the
bladder, is attached to the posterior surface
of the symphysis pubis above the origin of the
levator ani, and to the inner surface of the
ischiadic spine.
The perineal fascia is divided into two por-
tions, deep and superficial, which enclose be-
tween them the superficial muscles of the
anterior perineal group, and also the bulb of
the urethra and the crura of the penis. The
deep perineal fascia or triangular ligament is
subdivided into two layers, anterior and pos-
terior, which enclose between them the mem-
branous urethra, with its compressor muscles
and Cowper's glands. They are both attached
to the lower border of the pubic symphysis
and sub-pubic ligament, and to the inner
border of the united ischio-pubic rami, and
intervene between the posterior and anterior
perineal groups of muscles. The superficial
perineal fascia covers in the anterior perineal
region, and is attached to the anterior part of
the inner border of the ischio-pubic rami, and
to the anterior surface of the angle of the
pubis.
The crura of the penis, or, in the female,
those of the clitoris, may also be mentioned
as implanted on the rough inner border of the
ischio-pubic rami about their junction ; as
well as the round uterine ligament, in the fe-
male, to the anterior surface of the pubis.
MECHANICS OF THE HUMAN PELVIS.
When we consider the pelvis with regard to
its architectural adaptations, and compare it
with the principles of engineering, we are
struck with the beautiful simplicity of the
means by which it combines strength with
elasticity, and lightness with capacity and
unity of design. The weight of the trunk is
to be transmitted through the lumbar ver-
tebrae to the sacrum, and from thence to
points of support, which vary with the posi-
tion of the inferior extremities. In the erect
position, these points are the femora. In the
sitting position they are the tuberosities of
the ischia.
The experiments of Weber have proved
that though the centre of gravity of the
trunk itself (without the legs) is placed in
the transverse vertical plane as high as the
sterno-xiphoid joint, yet the centre of gravity
of the whole body, as marked by the point of
section of the before-mentioned transverse-
vertical with a horizontal plane, is placed only
PELVIS.
139
8'7 millimetres above the sacro-lumbar joint,
or just above the pelvic arch. All weight on
the arch, such as that of the trunk, is sup-
ported most easily when its line of gravity
falls through this part, and coincides with that
of the whole body in the transverse vertical
plane, and the trunk will be found to be
thrown into such a position, when supporting
heavy weights, as will tend to produce this
effect. And, according to the researches of
Ilokitanski, when the sacro- vertebral angle
and pelvic inclination is increased, as by hip
disease, there is always a compensatory curve
of the spine backward, to keep the centre of
gravity above this point.
In artificial constructions for the purpose
of transmitting a weight downwards from
a central to two lateral points, a segment of
a circle, or arch is most commonly made
use of, and generally consists of two lateral
curved portions, composed of separate parts
or voussoirs, with an interposed substance
between them called a keystone or crown-
piece, of a wedge shape, and placed with the
broad end uppermost. This wedge shape
exactly corresponds to the interval which
would be left between the lateral curved
pieces, having their ends cut square. Any
force operating on the keystone from above
tends only to drive the broader part of the
wedge further between the lateral pieces,
at the same time pressing them nearer to each
other, and so to increase the firmness of the
arch, so long as the extremities are firmly
fixed in the ground and prevented from start-
ing outwards, which is generally accomplished
by means of abutments.
Constructed upon this plan, the pelvis pre-
sents two lateral curved thickened buttresses
or columns, passing from the cotyloid to the
sacro-iliac articulations, and two others pass-
ing on a plane posterior to these from the
tuberosities of the ischia along their de-
scending rami, and through the ilia to the
same sacro-iliac articulations; and interposed
between each of these corresponding lateral
pieces is the common keystone of both the
arches thus formed, the wedge-shaped sacrum.
The sacrum thus forms the common cul-
minating point of two arches, viz., the cotylo-
sacral or standing arch, and the ischio-sacral
or sitting arch. And the planes of these two
arches are so directed as to coincide or be-
come applied to each other at the top of
the great sciatic notch, as may be seen by
reference to the diagram (fg. 86. A, a a').
In this comparison, however, it must be borne
in mind, that the extreme tenacity and strength
of the material used, bone, obviates the ne-
cessity of the use of many pieces in the
lateral portions, such as the "voussoirs" of
stone arches, and is more analogous to
the iron materials sometimes used for this
purpose. And it is in these lines of pressure
that we find the bulk and strength of the
osseous structure of the pelvis most displayed.
The span of the cotylo-sacral arch being
greater, and more elliptical in the female
than in the male, where it is almost circular,
renders them less able to support heavy weights;
and on account of the greater distance to
Fig. 86.
A, diagram of the pelvic arches b, a, b', cotylo-
sacral arch ; c, a, c 1 , ischio-sacral arch ; 5, d, I/,
cotylo-pubic tie ; c, d, d, ischio-pubic tie.
B, diagram of pelvic levers : c, a, line of gravity ;
F, b, pubic lever; F, w, cotylo-sacral lever;
w, P, posterior spinal or iliac lever ; F, c, direction
of spinal power ; w, c, direction of spinal weight ;
F, cotyloid fulcrum ; d, femoral support.
which it separates the femurs, contributes to
produce the waddling gait in running which
is characteristic of this method of female pro-
gression.
Instead of abutments to prevent the extre-
mities of the arch starting outwar.ls, we often
see, in artificial constructions, a connecting
link or tie extending between these extremi~
ties to hold them together, or the circle of
which the arch is a segment is completed
below, as in tunneling.
Such a tie and completion of the circle
we have in the horizontal rami of the pubic
bones, for the cotylo-sacral arch, and in the
united ischio-pubic rami, for the ischio-sacral
arch ; and they are connected in front, at
the pubic symphysis, exactly as these two
arches themselves are behind at the sacro-iliac
joints.
By the vertical ischio-pubic arch thus formed,
that portion of the pressure which has a tend-
ency to push forward and upward the extre-
mities of the ischio-sacral arch, is supported
and thrown upon the cotylo-sacral arch, the
whole weight of the trunk, in a sitting posture,
being thus divided between them The ischio-
pubic rami are the parts of the pelvis most
liable to fracture, according to Cruveilhier,
from the application of force acting on the
ischia.
The cotylo-pubic arch not only resists the
starting outward of the ends of the cotylo-
140
PELVIS.
sacral arch, but it resists their displacement
inwards, which would result from the pressure
of the femora in the direction of the necks of
these bones. The effect of this pressure, when
the pubes yield to it, is shown in the de-
formity which has been termed the rostrated
pelvis, resulting from the crushing of these
bones together. The cotylo-pubic arch also
receives, in its concavity, part of the weight
of the abdominal viscera, though, from the
attachment of these to the spine, their chief
weight is concentrated upon the common
centre of pelvic arches, the sacrum. The
ilia are also generally supposed to support
the intestines in a great measure ; but this
support, on account of their great obliquity in
the erect position, cannot be so important as
is commonly imagined, except, as in the case
of the coecum and rectum, through peritoneal
attachments. The human pelvis, when thus
taken .in conjunction with the thorax, forms
the base of a cone, the apex of which is
the neck, a disposition for supporting the
contained viscera which the erect position
demands, and which contrasts strongly with
the structure of quadrupeds.
Again, the cotylo-sacral and pubic arches
on each side, united at their extremities in
the acetabula, form two lateral arches, on the
centres of which rest the thigh bones. Against
the lateral pressure exercised by the thigh
bones, these two arches, connected, at their
anterior and posterior extremities, by the
symphysis pubis and sacrum, form, as Mayo
observes, an elastic hoop. The ischia also
contribute to this resistance against lateral
pressure, and form, with the two other por-
tions of the innominate bones, a sort of arched
tripod, on the apex of which the femur is
supported.
In addition to the buttresses already de-
scribed, there is, placed vertically above the
cotyloid cavity, a thick rib of bone, which
transmits to the arched crest of the ilium,
and through it and the sacro-iliac joint to
the sacrum, a portion of the direct vertical
pressure from the heads of the thigh bones.
This thickened portion of the iliac wing has
been mentioned in the general description
of the bone as impinging on the iliac crest
in the middle of its anterior curve. The
division of the pressure thus produced, no
doubt calls into action much more com-
pletely the elastic resistance of the pelvis,
in sudden increase of weight. Thus in
the sacro-iliac joint meet three buttresses
or thickened lines of pressure, of which the
direct cotylo-sacral is the central and principal
one, the ischio-sacral the lowest and next in
strength, and the superior or indirect cotylo'
sacred the weakest.
But, besides merely supporting quiescent
superincumbent weight, the pelvic arches are
required to resist and break the force of
shocks and concussions meeting with the
inertia of the trunk, and passing from the
lower extremities of the body to the vital and
delicate cranial and thoracic structures.
These dynamic requirements are met by pe-
culiar modifications of the simple arch, com-
bining with it, by an admirable adaptation,
the qualities of an elastic spring.
First, the cotylo-sacral arch, on which
the greatest number and force of shocks falls,
is not placed vertically, but obliquely upivards
and backwards, while the cotylo-pubic arch,
being united to it at its extremities, and con-
tinued in the same plane over the femoral
supports, forms the anterior arm of a bent
lever of the first order, of which the cotylo-
sacral arch is the posterior curved arm, the
spinal column the weight, and the heads of the
femurs the fulcrum (see Jigs. 87. and 86. B).
Fig. 87.
Drawing of a section of the pelvis in the cotylo-
sacral arch, removing the left iliac wing, a, a', line
of fulcrum falling in the transverse vertical plane
of trunk; c,c', line of weight passing through centre
of sacro-iliac joint ; b,V, line of power or pubic pro-
jection ; d, d 1 , line of sacral projection ; e,f, cotylo-
sacral curve ; a!, U, pubic arm of lever ; a', c', co-
tylo-sacral arm ; a', d', length of gluteal arm ; c', d',
posterior spinal arm; g, posterior iliac projec-
tion.
The anterior or pubic arm of this lever
giving insertion to the powerful extensor
muscles of the thigh, which represent the
power, is thrown upwards by the operation
of downward force on the crown of the
cotylo-sacral arch, calling these muscles into
contractile reaction, which overcomes gradu-
ally the force of any shock operating at the
posterior extremity of the pelvic lever over
the fulcrum of the thigh bones. In well-
formed male pelves, the pubic arm of this
lever is increased in power by being longer
than the cotylo-sacral by or of an inch,
the one being 2 inches, the other 1 inch, in
PELVES.
141
direct distance from the centre of the cotyloid
support (fig. 87. a' b' ', a' </).* This give's the
anterior muscles of the thigh greater power in
resisting the downward force of the trunk at
the sacral extremity of the lever.
But by the addition of the iliac and sacral
projections posteriorly, the cotylo-sacral arm
is increased in length by 2 inches, as will be
observed on reference to the figure (c', <T),
a disposition which evidently increases the
power of the glutei muscles in maintaining
the habitual erect position, and resisting any
tendency to fall forwards, by extending the
femora on the pelvis.
Again, if we follow the lateral curve of the
sacrum at the brim of the pelvis, we shall
find that it projects forward in the promontory
of the sacrum, immediately under the point
supporting the spine, so that its profile, taken
with that of the ilium, as seen in the figure
(cf), presents a curve with the concavity for-
ward, in the manner of a C spring. It is
worthy of remark, that, in the erect position,
a plumb line, dropped opposite to the centres
of the bodies of the axis and last lumbar ver-
tebra, passes across the centre of the sacral
promontory, and directly between the centres
of the cotyloid cavities, as was proved by the
experiments of Weber. Such a plumb line
marks exactly the line of the transverse
vertical plane of the spinal column before
mentioned, which, when continued down-
wards, passes through the sacral extremity of
the pelvic lever, and also through the cotyloid
fulcrum, dividing equally and vertically the
heads of the thigh bones, and crossing the
ischio-pubic rami about their suture (a a').
Thus, the oblique C-like curve of the cotylo-
sacral arch, or posterior bent arm of the lever,
meets this plane at its two extremities, di-
recting its concavity towards it like the arc
of a cirgle to its chord ; and contributes, by
its elastic reaction, to break the force of
shocks operating through the spine and fe-
mora. In deformed pelves, we generally find
that the sinking of the sacrum, the crown of
the pelvic arch, under the weight of the trunk,
produces an increased curvature of the iliac
bones forwards by the yielding of the C spring,
and thus still further encroaches upon the
dimensions of the pelvic brim.
The above considerations will illustrate the
fallacy of the deduction of Cruveilhier in re-
spect to the statics of the pelvis. This cele-
brated anatomist remarks, that " the arti-
culation of the vertebral column with the
pelvis is situated at the back part of that
cavity, while the articulation of the femurs is