brane is composed unite, as in the
scrotum, and form an imperfect septum. In front of the anus, beneath the
sphincter ani, the fascia degenerates into cellular membrane, one layer
of which is spread over the adipose tissue in the ischio-rectal space,
whilst its deeper and stronger layer unites with the deep perinaeal
fascia, and by this connexion separates the urethral from the anal
spaces. The superficial fascia of the hypogastrium, the scrotum, and the
perinaeum forming a continuous membrane, and being adherent to the
several parts above noticed, may be regarded as a general double sac,
which isolates the inguino-perinaeal region from the femoral and anal
regions, and hence it happens that when the urethra becomes ruptured,
the urine which is extravasated in the perinaeum, is allowed to pass
over the scrotum and the abdomen, involving these parts in consequent
inflammation, whilst the thighs and anal space are exempt. The tunicae
vaginales, which form the immediate coverings of the testicles, cannot
be entered by the urine, as they are distinct sacs originally protruded
from the abdomen. It is in consequence of the imperfect state of the
inguino-perinaeal septum of the fascia, that urine effused into one of
the sacs is allowed to enter the other.

Like all the other structures which join on either side of the median
line, the penis appears as a symmetrical organ, D D, Fig. 2, Plate 50.
While viewed in section, its two corpora cavernosa are seen to unite
anteriorly, and by this union to form a septum "pectiniforme;"
posteriorly they remain distinct and lateral, F F, Fig. 2, Plate 51,
being attached to the ischio-pubic rami as the crura penis. The urethra,
B, Fig. 2, Plate 50, is also composed of two sides, united along the
median line, but forming between them a canal by the cleavage and
partition of the urethral septum. All the other structures of the
perinaeum will be seen to be either double and lateral, or single and
median, according as they stand apart from, or approach, or occupy the
central line.

The perinaeum, Figs. 1, 2, Plate 51, is that space which is bounded
above by the arch of the pubes, behind by C, the os coccygis, and the
lower borders of, I I, the glutaei muscles and sacro-sciatic ligaments,
and laterally by D D, the ischiatic tuberosities. The osseous boundaries
can be felt through the integuments. Between the back of the scrotum and
the anus the perinaeum swells on both sides of the raphe, A B, F