408 THE MUSCULAR SYSTEM. 
The pubo-cavernosus is an occasional slip arising from the pubic ramus, and inserted into 
the dorsum of the penis. It corresponds to the levator penis of lower animals. 
The compressor urethre (constrictor urethra) constitutes the deeper muscular 
stratum of the perineum. It is placed on the pelvic aspect of the triangular 
ligament. It arises from the lower part of the pubic ramus, and is directed inwards, 
its fibres radiating so as to enclose the membranous urethra. It is inserted into a 
median raphe, partly in front of the urethra, but for the most part behind it. The 
fibres most intimately related to the urethra form a tubular sheath for the canal, 
and have no bony attachments. 
The most anterior and most posterior fibres of the compressor urethre exist sometimes 
as separate muscles. 
The transversus perinei profundus consists of a bundle of fibres on either side, 
arising from the ascending ramus of the ischium just below the compressor urethra. It 
is inserted into a median raphe continuous with that of the compressor urethra. The 
muscle in fact constitutes a separate bundle below and behind the compressor urethre. 
The ischio-pubicus is a term applied to a feeble bundle of fibres which, when 
present, lies above and in front of the compressor urethre. It arises from the pubic 
ramus, and is inserted into a median raphe in front of the membranous urethra. This 
muscle is homologous with the compressor vene dorsalis penis of lower animals. 
The compressor urethree in the female is smaller than in the male. Its 
insertion is modified by the relations of the urethra to the vagina. The anterior 
Corpus cavernosum 
(Cink 
Nerve to corpus = 
cavernosum —~———_ 
Nerve to dorsum = 
of penis 
COMPRESSOR URETHRA ——~— 
___— Bulb of penis 
SBR Triangular ligainent 
SS __ (anterior layer) 
a 
Nerve to bulb 
Triangular ligament 
(posterior layer) 
Internal pudic nerve 7— 
Crus penis 
N 
,— LEVATOR ANT 
Fic. 302.—THE TRIANGULAR LIGAMENT OF THE PERINEUM, AND THE TERMINATION OF THE PuDIC NERVE. 
fibres are continuous with those of the opposite side in front of the urethra; the 
intermediate fibres pass between the urethra and vagina, and the posterior fibres 
are attached, along with the transversus perinei profundus (transversus vagine), into 
the side of the vagina. 
NERVE SUPPLY. 
The pudic nerve (S. 2. 3. 4.) supplies all the muscles in this group; the external sphincter 
through the inferior hemorrhoidal, and the others through the perineal branch of the nerve. 
The external sphincter is also supplied by the perineal branch of the fourth sacral nerve. 
ACTIONS. 
The external sphincter closes the anal canal. The transversus perinei superficialis draws 
back and fixes the central point of the perineum, assisted by the external sphincter. The bulbo- 
cavernosus of the male constricts the bulb and corpus spongiosum, and so expresses the last drops 
i i”) ar. 
 —— te 
