isthmi urethrae;" and by M. Cruveilhier as being
part of the levator ani muscle. "As in one case," (observes Mr. Quain,)
"I myself saw a few vertical muscular fibres connected with the
transverse compressor, it has been thought best to retain the muscle in
the text."--Dr. Quain's Anat., Am. Ed. vol. ii. p. 539.]

[Illustration: Abdomen, showing blood vessels and other internal organs.]
Plate 55--Figure 3

Fig. 1, Plate 56, represents by section the natural forms of the urethra
and bladder. The general direction of the urethra measured during its
relaxed state from the vesical orifice to the glans is usually described
as having the form of the letter S laid procumbent to the right side
[capital S rotated 90 degrees right] or to the left [capital S rotated
90 degrees left]. But as the anterior half of the canal is moveable, and
liable thereby to obliterate the general form, while the posterior half
is fixed, I shall direct attention to the latter half chiefly, since
upon its peculiar form and relative position depends most of the
difficulty in the performance of catheterism. The portion of the urethra
which intervenes between the neck of the bladder, K, and the point E,
where the penis is suspended from the front of the symphysis pubis by
the suspensory ligament, assumes very nearly the form of a semicircle,
whose anterior half looks towards the forepart, and whose posterior half
is turned to the back of the pubis. The pubic arch, A, spans crossways,
the middle of this part of the urethra, G, opposite the bulb H. The two
extremes, F K, of this curve, and the lower part of the symphysis pubis,
occupy in the adult the same antero-posterior level; and it follows,
therefore, that the distance to which the urethra near its bulb, H, is
removed from the pubic symphysis above must equal the depth of its own
curve, which measures about an inch perpendicularly. The urethral
aperture of the triangular ligament appears removed at this distance
below the pubic symphysis, and that portion of the canal which lies
behind the ligament, and ascends obliquely backwards and upwards to the
vesical orifice on a level with the symphysis pubis in the adult should
be remembered, as varying both in direction and length in individuals of
the extremes of age. In the young, this variation is owing to the usual
high position of the bladder in the pelvis, whilst in the old it may be
caused by an enlarged state of the prostate. The curve of the ure