ing from one
ischio-pubic ramus to the other, whilst by its lower border,
corresponding with the line of the transversae perinaei muscles, it
becomes continuous with the superficial fascia, in the manner before
described. The deep perinaeal fascia (triangular ligament) encloses
between its two layers, C E, on either side of the urethra, the pudic
artery, the artery of the bulb, Cowper's glands, and some muscular
fibres occasionally to be met with, to which the name "Compressor
urethrae" has been assigned. At this stage of the dissection, as the
principal vessels and parts composed of erectile tissue are now in view,
their relative situations should be well noticed, so as to avoid
wounding them in the several cutting operations required to be performed
in their vicinity.

Along the median line (marked by the raphe) from the scrotum to the
coccyx, and close to this line on either side, the vessels are
unimportant as to size. The urethra lies along the middle line in the
anterior perinaeal space; the rectum occupies the middle in the
posterior space. When either of these parts specially requires to be
incised--the urethra for impassable stricture, &c., and the lower part
of the rectum for fistula in ano--the operation may be performed
without fear of inducing dangerous arterial haemorrhage. With the object
of preserving from injury these important parts, deep incisions at, or
approaching to, the middle line must be avoided. The outer
(ischio-pubic) boundary of the perinaeum is the line along which the
pudic artery passes. The anterior half of this boundary supports also
the crus penis; hence, therefore, in order to avoid these, all deep
incisions should be made parallel to, but removed to a proper distance
from this situation. The structures placed at the middle line, B M F,
Fig. 2, Plate 52, and those in connexion with the left perinaeal
boundary, D G L, require (in order to insure the safety of these parts)
that the line of incision necessary to gain access to the neck of the
bladder in lithotomy should be made through the left side of the
perinaeum from a point midway between M, the bulb, and D, crus penis
above, to a point, K, midway between the anus, F, and tuber ischii, G,
below. As the upper end of this incision is commenced over the situation
of the superficial perinaeal artery and the artery of the bulb, the
knife at this place should only divide the skin and superficial fascia.
The lower end, K, just clears the