PERINEAL MUSCLES IN THE MALE. 345 



The bnlbo-cavernosus or ejaculator nrinae muscle is united with its fellow 

 of the opposite side in a median tendinous raphe continued forwards from the 

 central point of the perineum, and the two muscles cover the bulb and the adjacent 

 part of the corpus spongiosum urethras. 



The fleshy fibres arise from the central point of the perineum and from the 

 median raphe, and are directed outwards and forwards on the surface of the corpus 

 spongiosum. The greater number ascend between the crus penis and the corpus 

 spongiosum, and end on the dorsum of the latter body by joining those of the 

 opposite side in a strong aponeurosis. At the fore part a small portion 6t the muscle 

 passes to the outer side of the corpus cavernosum, where it is attached in front of 

 the ischio-cavernosus, sending also a tendinous expansion over the dorsal vessels of 

 the penis ; and the posterior fibres, shorter than the anterior, are inserted by the 

 side of the bulb into the under surface of the triangular ligament. 



The fibres which invest the most prominent part of the bulb are more or less distinct from 

 those contiguous to them, and have been described by Kobelt as forming a separate muscle, to 

 which he has given the name compressor hemispheerium bulbi. The fibres of this muscular 

 slip are connected by a small tendon, above the urethra, with the corresponding part of the 

 opposite side. 



The constrictor or compressor urethras muscle consists of fibres attached on 

 each side to the ischio-pubic rami, as well as to the adjacent surfaces of the fascial 

 layers between which it is enclosed, and extending for the most part transversely 

 across the subpubic arch, some of them in front of, and others behind, the mem- 

 branous part of the urethra, for which they form a kind of sphincter. In some 

 bodies a median tendinous raphe divides the muscle more or less completely into 

 lateral halves. The hindmost fibres of this muscle are sometimes described separately 

 under the name of transversus perinei profundus. 



While the greater number of the muscular fibres contained between the layers of the tri- 

 angular ligament pass transversely from side to side as above stated, there are usually to be 

 recognized, especially in well-developed subjects, other collections which tiike different direc- 

 tions. Thus, one set of fibres passes obliquely from behind forwards and inwards ; another 

 set surrounds the urethra circularly ; and on the inferior surface of the constrictor muscle a 

 longitudinal slip of variable breadth extends from apex to base of the triangular ligament. 

 All these bundles are, however, intimately connected together, and pass gradually into one 

 another, so that they cannot properly be regarded as forming distinct muscles. The longi- 

 tudinal fasciculi described by Wilson as passing from the pelvic surface of the pubis on each 

 side, and meeting behind the membranous part of the urethra, have not been generally recog- 

 nized by succeeding anatomists. (On the arrangement of the constrictor urethras muscle, as 

 well as of the other muscles and fascise of the perineum, see Lesshaft, " Ueb. einige d. 

 Urethra umgebenden Muskeln und Fascien," Arch. f. Anat., 1873 ; Cadiat, "Etude sur les 

 muscles du perinee en particulier sur les muscles dits de Wilson et de Guthrie," Joum. de 

 1'anat., 1877 ; Holl, " Ueb.d. Verschluss des mannl. Beckens." Arch. f. Anat., 1881 ; Tschaussow, 

 " Resultate makro- und mikroskopischer Untersuchungen lib. d. tief en Muskeln d. vord. Dammes 

 b. Manne u. iib. d. Verhalten d. Venen zu ihnen," Arch. f. Anat., 1883 ; Cros, " Rech. anat. sur 

 les muscles de Wilson et de Guthrie," Montpellier, 1887.) 



Relations. The constrictor urethras is separated from the levator ani by the upper layer, 

 and from the superficial muscles of the fore part of the perineum by the lower layer of the 

 triangular ligament. Embedded in the substance of the muscle on each side at its origin from 

 the bone are the pudic vessels and the dorsal nerve of the penis, and more mesially are the 

 vessels of the bulb and the gland of Cowper. 



Within the constrictor muscle the membranous part of the urethra is surrounded 

 by involuntary muscular fibres which form part of its proper wall, and will therefore 

 be referred to in the description of the reproductive organs in Yol. III. 



Nerves. The external sphincter receives offsets from the fourth sacral nerve and the 

 inferior hsemorrhoidal branch of the pudic nerve ; the levator ani from the fourth 

 sacral and the perineal branch of the pudic ; and the coccygeus from the fourth sacral 

 nerve. 



