926
PERINEUM.
ing portion of the urethral canal, explain this
sufficiently ; nor should it be forgotten that the
muscular girth formed by the acceleratores
urinæ is often the seat of spasm.
The error in catheterism of most frequent
occurrence here is the perforation of the floor
of the urethra at the bulb, after which the ex¬
tremity of the instrument passes between the
rectum and the urethra. The surgeon commits
this mistake by neglecting to depress the handle
of the catheter in time to raise the point out of
the sinus of the bulb into the membranous
portion, and so much the more readily as the
slightest force exercised in this wrong direction
is sufficient to perforate the spongy tissue.
The premature depression of the handle of
the catheter may likewise injure the urethra,
but in a different manner, for if that ma¬
nœuvre be executed too soon and with undue
force, the point of the instrument will lacerate
the upper wall of the canal anterior to the tri¬
angular ligament.
A difficulty may, however, be experienced
in entering the membranous portion of the
urethra, even though the handle of the catheter
be depressed at the proper time ; the surgeon
in such cases fails to “ hit off” the aperture in
the triangular ligament which transmits the
urethra, and the point of the instrument swerv¬
ing laterally, comes to press against the front of
the triangular ligament at one side of the orifice,
instead of traversing the orifice itself. To guard
against such a casualty, care must be taken to
keep the point of the catheter fairly in the
middle line, and (should any obstruction arise)
to exercise slight traction upon the penis for the
purpose of rendering tense the fibrous covering
of the bulb, and in that manner stretching the
opening in the triangular ligament.
From these principles it clearly follows that,
except under peculiar circumstances, curved
instruments are to be preferred, for their adapta¬
tion to the curvature of the canal enables them
to reach the bladder without exercising undue
pressure upon any part of the passage ; whilst
the straight staff conducted ever so skilfully
must to a certain extent strain or disturb the
permanently curved portion of the urethra.
But, besides this obvious advantage, the natural
impediments to catheterism (placed chiefly
along the floor of the passage) are also most
easily surmounted by the curved instrument,
for its point can at any moment be readily
raised by the operator, whilst he accomplishes
the same object much more imperfectly in
using the straight staff. It cannot be denied,
however, that, for certain purposes, straight
instruments possess a decided superiority, and
therefore every surgeon should be prepared to
employ them when the occasion suits.
The preceding outline describes with suffi¬
cient accuracy the course and relations of the
principal organs belonging to the perineum,
and therefore it now only remains to study the
anatomy of this region from below, according to
the usual method of dissection. The subject is
of course supposed to be placed in the ordinary
position, with a full-sized staff introduced into
the bladder, the rectum artificially distended,
the scrotum raised and drawn forwards, the |
hands bound firmly to the ankles at each side 1
respectively, the pelvis elevated on a block, and |:
the knees separated to a convenient distance |
from each other.
Prepared in this manner, the perineum pre- ‘
sents anteriorly a well-marked median promi- :
nence corresponding to the urethra, and which ,
for obvious reasons enlarges considerably in
the living subject during erection. At either
side of this urethral prominence a parallel de¬
pression exists, external to which the resisting
edges of the rami of the ischium and pubis may J
be always readily recognised by the finger. At
the posterior part of the perineum the point of
the coccyx may be felt distinctly in the middle
line ; the tuberosities of the ischia covered by a
great depth of soft parts project remarkably at
the sides, constituting the extreme lateral limits
of the region, whilst the mid space between
these eminences exhibits a deep depression
containing the anus. In front of the anus a
central elevation of the skin termed the raphe
extends forwards along the perineum, and may
be traced distinctly to the scrotum and penis ; 4
it serves as a guide to the surgeon in many
operations, pointing out the middle line accu¬
rately so long as the integuments retain their
normal relations.
Integument.—The characters of the cuta¬
neous covering of the perineum are not uniform
throughout ; in some situations its thickness is
very considerable, whilst in others it appears
remarkably delicate. In front the skin becomes
gradually finer as it approaches the scrotum,
and at the margins of the anus its delicacy is
extreme ; but in the neighbourhood of the
tuber ischii and along the edge of the gluteus
maximus it possesses great density and offers
considerable resistance to the scalpel : at the
circumference of the region it in fact gradually
assumes the properties of the neighbouring te¬
gumentary membrane, resembling that of the
scrotum anteriorly, merging insensibly into the
integument of the buttock and thigh laterally,
and even approaching to the characters of mu¬
cous membrane in the vicinity of the gut ; it is
generally of a dark brown colour in the healthy
adult, and of a lighter hue in the child ; but
there are in this respect numerous individual
varieties ; the darker the teint the more highly
developed usually are the subjacent muscles.
Cutaneous follicles abound in the perineum
and occur in greatest numbers near the anus and
at the root of the scrotum, where their secre¬
tions are most required. The skin around the
anus is thrown into rugae disposed in a radiated
manner, and which produce a puckered appear¬
ance so long as the orifice remains contracted :
they disappear during its dilatation, and are de¬
signed to favour the extreme distension to which
the anal extremity of the intestine is occasion¬
ally subjected during defaecation. The folds in
question become at times the seat of fissure,
ulceration, or excrescence, which may demand
surgical interference for their relief.
In the lateral operation of lithotomy the first
incision should commence at the left side of the
raphe, about an inch or an inch and a quarter