1 66 ABDOMEN 



fully defined, clean, on each side, the ischio-cavernosus muscle 

 which covers the superficial surface of the crus penis. Follow 

 it backwards to its origin from the medial aspect of the posterior 

 portion of the ramus of the ischium. Then clean the superficial 

 transverse muscle, which springs from the same point, and follow 

 it to its insertion into the central point of the perineum. Next 

 clean the bulbo-cavernosus muscle. Note that it springs from 

 the central point of the perineum and from a fibrous raphe on 

 the superficial surface of the bulb of the urethra. Trace its 

 posterior fibres round the sides of the bulb to the superficial 

 surface of the inferior fascia of the urogenital diaphragm to 

 which they are attached. Note (i) that the middle fibres 

 pass round the sides of the corpus cavernosum urethrae and 

 blend with the muscle of the opposite side on its dorsal surface, 

 ventral to the anterior ends of the crura penis. (2) That 

 the anterior fibres pass round the sides of the corpus caver- 

 nosum penis and blend with their fellows of the opposite side 

 on the dorsum of the penis. The arrangement of the fibres 

 shows quite clearly that when the muscles of the two sides act 

 together they must compress the bulb of the urethra, the corpus 

 cavernosum urethrae and the corpus cavernosum penis. 



After the superficial perineal muscles have been examined 

 divide the superficial transverse muscle, turn it aside, and attempt 

 to find the terminal twigs of the deep branch of the perineal 

 nerve which pass deep to the superficial transverse muscle and 

 are distributed to that muscle, to the bulbo- and ischio-cavernosus 

 muscles, and to the bulb of the urethra. Next detach the crus 

 penis from the rami of the pubis and ischium, and the superficial 

 surface of the inferior fascia of the urogenital diaphragm. 

 Commence at its posterior end, pass carefully forwards until the 

 profunda artery of the penis is found piercing the inferior fascia 

 of the urogenital diaphragm and entering the crus. Clean that 

 artery for a short distance, and secure the dorsal artery and 

 dorsal nerve of the penis which pierce the inferior fascia of the 

 urogenital diaphragm close to the profunda artery. Then turn 

 to the bulb of the urethra. Detach the posterior end of the bulb 

 from the central point of the perineum, and turn it carefully 

 forwards until the urethra is found entering it in the median 

 plane, and an artery on each side. The arteries are the arteries 

 to the bulb, from the internal pudendal arteries. Do not injure 

 either the arteries or the urethra, but clean the superficial surface 

 of the inferior fascia of the urogenital diaphragm, and then 

 proceed to the study of the structures exposed. 



Superficial Perineal Muscles. Under this heading are 

 included not only the bulbo-cavernosus and ischio-cavernosus 

 muscles, but also the superficial transverse perineal muscles. 

 The superficial perineal muscles have been seen to lie within 

 the pouch formed by the fascia of Colles and the inferior 

 fascia of the urogenital diaphragm. Each muscle is invested 

 by its own delicate layer of deep fascia. 



M. Transversus Perinei Superficialis. The superficial 

 transverse perineal muscle is a narrow slip of muscular fibres 



