THE MUSCLES OF THE PERINEUM. 407 
the corrugator cutis ani (a series of non-striated muscular fibres radiating from the 
anal opening). It rests on the edge of the levator ani, and forms the median 
boundary of the ischio-rectal fossa. 
The transversus perinei superficialis is not always present. It consists of a 
more or less feeble bundle of fibres, arising from the ascending ramus of the ischium 
and the fascia over it, and from the base of the triangular ligament. It is inserted 
into the central point of the perineum. It conceals the base of the triangular 
ligament, and has a variable relation to the superficial perineal vessels and nerves. 
The bulbo-cavernosus (ejaculator urine) surrounds the bulb, corpus spongiosum, 
and root of the penis. It is sometimes separated into two parts—posterior (com- 
pressor bulbi), and anterior (compressor radicis penis). It arises from the central 
point of the perineum, and from a median raphe on the under surface of the bulb 
and corpus spongiosum. The muscular fibres are directed outwards and forwards, 
and have a triple insertion: from behind forwards, (1) into the under surface of the 
triangular ligament; (2) into the membrane covering the corpus spongiosum ; and, 
(3) after encircling the corpora cavernosa, into the fascia coveri ing the dorsum of the 
penis. 
The ischio-bulbosus, not always present, arises from the ischium, and passes 
obliquely inwards and forwards over the bulbo-cavernosus, to be inserted inte the raphe 
superficial to that muscle. It belongs to the same stratum as the transversus perinei and 
erector penis. 
The compressor hemispherium bulbi is frequently absent. It consists of a 
thin cap-like layer of 
muscular fibres sur- = 
rounding the extremity 
of the bulb under cover 
of the bulbo-cavernosus. 
ERECTOR 
CLITORIDIS 
The bulbo-caver- 
nosus (sphincter va- 
gine) in the female is 
separated into lateral 
halves by the vaginal 
and urethral openings. 
It forms two thin 
layers covering the 
vaginal bulbs, and 
arises behind the 
vaginal orifice from 
the central point of 
the perineum. An- 
teriorly it is inserted 
into the root of the 
clitoris, some of its 
fibres embracing the 
corpora Gavernosa so 
as to reach the dorsum 
of the clitoris. 
= Ww] | ese 
=~ \ 
( \ i\ \ 
LEVATOR ANI 
2 o - = = = GLUTEUS 
The ischio-caver- MAXIMUS 
nosus (erector penis) Ls 
covers the crus penis. SPHINCTER ANI EXTERNUS 
It arises from the Fic. 301.—THE MUSCLES OF THE FEMALE PERINEUM (after Peter 
ischial tuberosity and Thompson). 
the great sacro-sciatic 
ligament, and passing forwards, is inserted by a fascial attachment into the under 
surface of the crus penis, and into the outer side and dorsal aspect of the corpus 
cavernosum. 
The ischio-cavernosus (erector clitoridis) in the female has a similar disposition, 
but is of much smaller size than in the male. 
