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