The urethra, at its membranous part, M, Fig. 1, Plate 53, which
commences behind the bulb, perforates the centre of the deep perinaeal
fascia, E E, at about an inch and a half in front of F, the anus. The
anterior layer of the fascia is continued forwards over the bulb, whilst
the posterior layer is reflected backwards over the prostate gland.

Behind the deep perinaeal fascia, the anterior fibres of K, the levator
ani muscle, arise from either side of the pubic symphysis posteriorly,
and descend obliquely down wards and forwards, to be inserted into the
sides of N N, the rectum above the anus. These fibres of the muscle, and
the lower border of the fascia which covers them, lie immediately in
front of the prostate, C C, Fig. 2, Plate 53, and must necessarily be
divided in the operation of lithotomy. Previously to disturbing the
lower end of the rectum from its natural position in the perinaeum, its
close relation to the prostate and base of the bladder should be
noticed. While the anus remains connected with the deep perinaeal fascia
in front, the fibres of the levator ani muscle of the left side may be
divided; and by now inserting the finger between them and the rectum,
the left lobe of the prostate can be felt in apposition with the
forepart of the bowel, an inch or two above the anus. It is owing to
this connexion between these parts that the lithotomist has to depress
the bowel, lest it be wounded, while the prostate is being incised. If
either the bowel or the bladder, or both together, be over-distended,
they are brought into closer apposition, and the rectum is consequently
more exposed to danger during the latter stages of the operation. The
prostate being in contact with the rectum, the surgeon is enabled to
examine by the touch, per anum, the state of the gland. If the prostate
be diseased and irregularly enlarged, the urethra, which passes through
it, becomes, in general, so distorted, that the surgeon, after passing
the catheter along the urethra as far as the prostate, will find it
necessary to guide the point of the instrument into the bladder, by the
finger introduced into the bowel. The middle or third lobe of the
prostate being enlarged, bends the prostatic part of the urethra
upwards. But when either of the lateral lobes is enlarged, the urethra
becomes bent towards the opposite side.

By dividing the levator ani muscle on both sides of the rectum, F, Fig.
2, Plate 53, and detaching and depressing