PENIS. 



915 



meatus; it terminates by several ramified ducts 

 in the submucous tissue of the canal. The 

 mucous membrane of the urethra is separated 

 from the tissue of the corpus spongiosum by a 

 moderately thick fibrous layer, winch is conti- 

 nuous with the external tunic of the spongy 

 body. 



Sir Everard Home conceived that the exter- 

 nal tunic of the canal of the spongy portion of 

 the urethra was muscular, and stales with re- 

 gard to it : " the muscular covering by which 

 the membrane is surrounded or enclosed is 

 made up of fasciculi of very short fibres, which 

 appear interwoven together and to be connected 

 by their origins and insertions with one another; 

 they have all a longitudinal direction." " The 

 fasciculi are united together by an elastic sub- 

 stance of the consistence of mucus." Sir E. 

 Home is mistaken with regard to the muscu- 

 larity of the external tunic of the spongy urethra, 

 but his description, as it relates to the disposi- 

 tion of the fibrous tissue, is correct. Indeed it 

 is evident that it is to this tissue that Sir E. 

 Home alludes, from a subsequent passage in 

 his essay, wherein he identifies his muscular 

 coat with the fibrous lining of the canal of the 

 corpus spongiosum. Thus he writes : " Im- 

 mediately beneath the muscular portion of the 

 urethra is the cellular structure of the corpus 

 spongiosum." And this inference is still fur- 

 ther corroborated by his belief that the external 

 fibrous tunic of the corpus cavernosum has also 

 " an admixture of muscular fibres." 



The muscles of the penis are, the erectores 

 penis, acceleratores urinae, ischio-bulbosi, and 

 compressores vense dorsalis. 



The erector penis (m. ischio-cavernosus) is 

 the muscle of the corpus cavernosum. It arises 

 by tendinous fibres from the anterior part of the 

 tuber ischii, from the internal border of the 

 ramus of the ischium, and from the root of the 

 cms penis ; it then curves in an oblique direc- 

 tion around the corpus cavernosum, and termi- 

 nates partly by becoming inserted into the side 

 of that body, and partly by a tendinous apo- 

 neurosis, which is continuous with a similar 

 aponeurosis derived from the opposite muscle. 

 In the first part of its course the muscle is ten- 

 dinous; where it is spread out on the crus 

 penis and corpus cavernosum it forms a thin 

 fleshy layer, which is prolonged for about one- 

 third along the penis, while in the rest of its 

 extent it is again tendinous, and constitutes the 

 thin aponeurosis above described. The erector 

 penis appears to effect its action as an erector 

 by compressing the crura and vena dorsalis, 

 and is aided in this office by the connection of 

 its aponeurosis by means of the suspensory 

 ligament with the symphysis pubis. When 

 called into exercise both muscles act together, 

 and by their united action embrace the root of 

 the penis, and strongly compress it. The effect 

 of pressure on the vena dorsalis must obviously 

 be to impede the return of the venous blood 

 from the penis, and the compression of the 

 crura produces the same result on the veins of 

 the corpus cavernosum. 



The acceleratores uritKE (m. bulbo-caverno- 

 sus) are the muscles of the corpus spongiosum ; 



they are situated on the posterior third of that 

 body, and form a thin muscular plane which 

 surrounds its cylinder, and is spread out upon 

 the under surface of the bulb. Each muscle 

 arises from the posterior border of the deep 

 perineal fascia at the middle line, and from a 

 median raphe which is closely adherent to the 

 under surface of the bulb and corpus spongio- 

 sum, and which connects it with its fellow of 

 the opposite side. From this extensive origin 

 the fibres of the muscle pass obliquely out- 

 wards and forwards, the most posterior to be 

 inserted into the ramus of the ischium and 

 pubis, the middle and most numerous to en- 

 circle the corpus spongiosum, and uniting by 

 tendinous fibres with the muscle of the opposite 

 side upon the upper surface of that body, to be 

 inserted into the inferior groove of the corpus 

 cavernosum ; and the anterior forming a narrow 

 fasciculus to pass outwards upon the corpus 

 cavernosum and be inserted into its fibrous 

 tunic and into the fascia penis. The posterior 

 fibres are almost transverse in their direction, 

 and cross the triangular interval between the 

 bulb and crus penis, being separated from the 

 deep perineal fascia by the superficial perineal 

 vessels and nerve, and by the ischio-bulbosus 

 muscle when it exists. 



The acceleratores are well calculated to con- 

 tract forcibly the canal of the urethra, and thus 

 to communicate an expulsive impetus to the 

 stream of urine or seminal secretion passing 

 along the tube. The expulsive action of these 

 muscles is made sensible to the hand when we 

 withdraw a catheter ; and the strength of its 

 gripe, when the catheter has been lodged in 

 the bladder. Indeed their complete contraction 

 constitutes an impassable though temporary 

 obstruction to the passage of the catheter along 

 the urethra, and gives rise to that form of 

 impediment which is known by the name of 

 spasmodic stricture. The contraction of these 

 muscles, moreover, acting suddenly on the 

 urethra, serves to expel the last portions of 

 urine and seminal secretion. Besides the in- 

 fluence which they exert on the urethra, the 

 acceleratores urince also enact the part of erec- 

 tors of the penis, by producing so much pressure 

 on the bulb and posterior part of the corpus 

 spongiosum as may impede the return of blood 

 through the venae corporis spongiosi, and at 

 the same time press forwards the contents of 

 the venous plexus of the bulb into the anterior 

 part of the corpus spongiosum and glans penis; 

 and their action in this respect is increased by 

 the tension made by their anterior fasciculi on 

 the fascia penis, and through it on the vena 

 dorsalis. 



The ischio-bulbosus (in. transversus perinei 

 alter; m. transversus perinei profundus) is a 

 small fan-shaped muscle situated in the trian- 

 gular interspace between the bulb of the urethra 

 and crus penis, and is not unfrequently want- 

 ing. It arises by a pointed origin from the 

 ramus of the ischium, and passing obliquely 

 inwards across the triangular space above des- 

 cribed, spreads out into a thin fan-shaped plane, 

 and is inserted into the fibrous tunic of the 

 bulb. On one occasion I found this muscle 



3 N 2 



