PERINEUM. 
est deviation to either side brings the correspond - 
ing vas deferens and vesicula seminalis into 
peril. In the majority of full-grown subjects 
the space under consideration is about three 
inches distant from the anus, so as to permit 
the index finger of the operator to reach it 
without difficulty; but from statements already 
made the reader will perceive that many excep- 
tions to this rule may be encountered in prac- 
tice. Again, the sides and base of this triangle 
(so long as the neighbouring parts remain in 
situ) are in general each of them respectively 
less than one inch in length; yet when thee 
bladder is removed from the subject and artifi- 
cially distended, and when the connections of 
the peritoneum are disturbed by dissection, the 
space to which we refer becomes immensely 
enlarged, and the anatomist is then apt to form 
a most exaggerated and erroneous idea of its 
natural dimensions. 
Against the recto-vesical paracentesis many 
very serious objections may be raised. In 
early life it should not be attempted, because 
at that period the peritoneum descends so low, 
and the under surface of the bladder is so little 
developed, that injury to the serous membrane 
of the abdomen would almost necessarily en- 
sue. Even in the adult the great uncertainty 
of the depth of the peritoneal cul-de-sac, added 
to the utter impossibility of ascertaining its 
extent in the living subject, constitutes a weighty 
argument against the operation ; whilst the 
enlarged prostate (so very common in old men) 
must frequently forbid its performance in after 
life; and the danger of wounding the vas 
deferens or the vesicula seminalis, or of pro- 
ducing urinary infiltration or a permanent fis- 
tula, may be fairly urged against this mode of 
relieving the bladder, at whatever age under- 
taken. The other methods employed for the 
same purpose in extreme cases of retention of 
urine are also no doubt open to valid objec- 
tions, but any further consideration of this 
subject would be out of place in the present 
article. 
In order to perform lithotomy successfully, 
or to tap the bladder with safety, the surgeon 
should ever bear in mind the direction of the 
axis of that organ. In the adult male the axis 
of the bladder runs nearly parallel to the axis 
of the upper strait of the pelvis; but upon a 
_ lower plane, that is to say, nearer to the pubis, 
if produced, it would pass superiorly through 
the linea alba between the umbilicus and the 
pubis, and it would touch the inferior extre- 
mity of the coccyx below. In the child its 
direction is very variable, for the urinary reser- 
voir being then in the abdomen and in contact 
with the anterior wall of that cavity, must 
‘necessarily move in obedience to the abdominal 
muscles, and every change of position which 
‘the bladder undergoes exerts a marked influ- 
ence upon its axis. During childhood the axis 
of the bladder appears in the dead subject to run 
from before backwards nearly horizontally, be- 
€ause the distended bladder, no longer sup- 
ported by the abdominal muscles, turns for- 
wards over the pubis; but in the living child, 
923 
when the recti abdominis are forcibly con- 
tracted, the line in question becomes nearly 
vertical. 
Tue vuREeTHRA.— Anatomists describe the 
urethra as a canal presenting a double curva- 
ture, of which the anterior segment is highly 
moveable, and of which the posterior is in a 
great measure fixed. The anterior segment 
(comprising the spongy portion of the urethra 
from the meatus urinarius to the vicinity of the 
bulb) exhibits, in the flaccid condition of the 
penis, a marked curvature concave downwards, 
which disappears, however, during erection, and 
which exerts little influence upon catheterism, 
since the surgeon easily obliterates it by raising 
the penis until it forms an angle of about forty 
degrees with the anterior wall of the abdomen. 
The posterior segment (consisting of the whole 
of the prostatic and membranous portions of 
the urethra, and also of the posterior part of 
its spongy portion) presents on the contrary a 
permanent curvature concave upwards, and 
belonging essentially to the perineum, it re- 
quires in this place a special description. To 
dissect the perineal portion of the urethra with 
advantage, the anatomist ought to remove the 
greater part of the ossa pubis and the ascending 
rami of the ischia from a recent subject, with 
the penis, the bladder, and the rectum attached ; 
this can be easily accomplished by cutting the 
herizontal ramus of the pubis at each side 
perpendicularly with a saw as near the aceta- 
bulum as possible, after which the instrument 
may be made to traverse the foramen ovale, 
and divide the ramus of the ischium in the 
immediate vicinity of its tuberosity. If the 
bladder be then inflated from one of the ureters, 
and the rectum distended, the preparation will 
exhibit in a satisfactory manner the urethra and 
many other parts described in this article, of 
which but an imperfect view is obtained in 
the ordinary dissection of the perineum from 
below. 
The posterior segment of the urethra repre- 
sents a reversed arch, of which the centre lies 
about ten lines beneath the symphysis pubis, 
whilst the extremities incline upwards, the one 
in front and the other behind the symphysis. 
Ample provisions exist to render this arch per- 
manent; its centre, constituted by the mem- 
branous portion of the urethra, is transmitted 
through the triangular ligament, and adheres 
by its circumference to the edges of the opening 
through which it passes; its posterior extre- 
mity, formed by the prostatic urethra, is tied 
up to the back of the pubis by the anterior true 
ligaments of the bladder, whilst the true sus- 
pensory ligament of the penis in front, and the 
prolonged attachments of the crura penis, pin- 
ning that organ up to the anterior surface of the 
pubis, raise the spongy portion of the urethra 
at its commencement, and consequently elevate 
the anterior extremity of the arch. The per- 
manency of this arch depends of course mainly 
upon the strength and resistance of the afore- 
said ligaments ; yet, although the properties of 
these structures are well known to anatomists, 
a difference of opinion prevails as to the pos- 
