508 DISSECTION OF THE PELVIS. 



the canal forms a second bend with the concavity downwards, but if tl-e 

 penis is raised the tube makes but one curve. The canal is divided into 

 three parts prostatic, membranous, and spongy. 



The prostatic part (b) is contained in the prostate gland, and receives 

 its name from that circumstance. Its length is about one inch and a 

 quarter, and in the erect posture it is inclined downwards to the triangular 

 perinaeal ligament. Its connections are the same as those of the gland 

 (p. 507). 



The membranous part (c), about three-quarters of an inch long, inter- 

 venes between the apex of the prostate and the front of the perinaeal trian- 

 gular ligament. It slants downwards in the erect posture to the lore part 

 of the triangular ligament ; and as the bulb of the next portion of the 

 urethral tube is directed backwards below it, the under part measures 

 only half an inch. 



This division of the urethra is the weakest : but it is supported by the 

 triangular ligament (). Surrounding it are the muscular fibres of the 

 constrictor urethrae ; and close below it are Cowper's glands with the 

 rectum. 



The spongy part (d) is so named from its being surrounded by a cellu- 

 lar and vascular structure. It is applied to and assists to form the body 

 of the penis, arid terminates anteriorly in the orifice named meatus uri- 

 narius in the end of the glands. It is the longest part of the urethra, and 

 measures about six inches. At its commencement this division of the 

 excretory canal is covered for two inches by the ejaculator urinae muscle 

 (fig. 130). 



The curve of the urethra is the fixed bend at the inner extremity, which 

 lies below the pubes. It extends from the bladder to an inch and a half 

 in front of the triangular ligament, and consists of the prostatic and mem- 

 branous portions, with a fourth of the spongy part. Its covexity, which 

 is turned downwards, is greatest at the fore part of the triangular ligament 

 in the erect posture : and from this point it curves up and back to the 

 bladder, and up anteriorly to the penis. 



It is surrounded by voluntary and involuntary muscular fibres : thus, 

 behind the ligament, by the involuntary muscular tissue of the prostate ; 

 within the ligament by the voluntary constrictor urethra, with a thin in- 

 voluntary layer inside that muscle ; and before the ligament by the volun- 

 tary ejaculator urinae. 



Its size is smallest where the tube pierces the perinaeal ligament (n), 

 and lies between the layers ; and is largest in the middle of the prostatic 

 part. 



Dissection. The tegumentary covering of the penis may be removed, 

 to see the component parts of that body ; and after its removal the spongy 

 part of the urethra will be better seen: the teguments should be replaced 

 after the part has been learnt. 



The PENIS is attached to the fore part of the pelvis, and hangs in front 

 of the scrotum. It is constructed of two firm fibrous bodies (fig. 174, e) 

 named corpora cavernosa, which are filled with a plexus of vessels, and 

 make up the principal part. Below these is a soft spongy substance 

 (corpus spongiosum) which surrounds the urethra, and forms the head or 

 the glans penis. The tegumentary investment, which covers the whole, 

 is noticed at p. 407. 



The body of the penis is grooved above and below along the middle 

 line, and is covered anteriorly by the glans penis; along its under suri'ace 



