SUPERFICIAL MUSCLES OF ANTERIOR HALF. 247 



aponeurosis over the inner and outer surfaces of the crus penis. It 

 rests on the root of the penis and the bone. 



//. The muscle compresses the crus penis against the sub- use 

 jiiix-nt bone, and retards the escape of the blood from the corpus 

 cavernosum by the veins, and in that way it contributes to the 

 erection of the organ. 



The EJACULATOR URix.E (bulbo-cavernosus) lies on the urethra. Ejaculator 

 The muscles of opposite sides arise from a median tendinous raphe ur 

 for 2i inches along the middle line, and from the central point of the 



perineum. The fibres are directed outwards, curving round the con- origin at 



c i i j XT. i i i i ^.u middle line 



vexity of the urethra, and give rise to a thin muscle, which has the 



following insertion : The hindmost fibres end on the lower surface of 



the triangular ligament. The anterior fibres, which are the longest and 



best marked, are inserted into the penis on its outer aspect, in front insertion by 



of the erector and send a tendinous expansion over the dorsal vessels 



of the penis. The intervening fibres, forming the greater part of the 



muscle, turn round the urethra, surrounding it for two inches, and 



join their fellows in a common tendon (fig. 92, p. 241). 



The ejaculator muscle covers the bulb and the corpus spongiosum surrounds 

 for nearly three inches below and in front of the triangular liga- t 

 ment. If the muscle be cut through on the left side and turned 

 off the urethra, the junction with its fellow above the tube will be 

 apparent. 



Action. The two halves, acting as one muscle, can compress the use, 

 urethra, and forcibly eject its contents. During the flow of fluid in 

 micturition the fibres are relaxed, but they come into use at the end voluntary 

 of the process, when the passage has to be cleared. The action is and invohm- 

 involuntary in the emission of the semen. 



The TRANSVERSUS PERINEI (fig. 93, c) is a small thin muscle, Transversus 

 which lies across the perineum opposite the base of the triangular pe 

 ligament. Arising from the inner side of the ischial tuberosity at origin ; 

 the fore part (fig. 92, p. 241), it is inserted into the central point of ends in 

 the perineum with the muscle of the opposite side, and with the point ; 

 sphincter ani and the ejaculator urinae. In a well-developed muscle 

 some of the fibres are partly continuous with the opposite part of the 

 external sphincter. Behind this muscle the superficial fascia curves 

 round to join the triangular ligament. 



Action. From the direction of the fibres the muscle will draw us e. 

 backwards the central point of the perineum, and help to fix it pre- 

 paratory to the contraction of the ejaculator. 



Sometimes there is a second small fleshy strip in front, of the Accessory 

 transversalis, which has been named transrcrsalis alter ; this throws muscle. 

 itself into the ejaculator muscle. 



TRIANGULAR SPACE. The three muscles above described, when A triangular 

 separated from each other by dissection, limit a triangular space, tween the 



of which the ejaculator urina3 forms the inner boundary, the erector 

 penis the outer side, and the transversus perinei the base. In the 

 floor of this interval is the triangular ligament of the urethra, with the knife 

 the superficial periueal vessels and nerves. The knife entering the may enter 



