PENIS. 853 



prostate gland below its middle lobe. The membranous division 

 extends from the prostatic portion to the ischial arch, and is the 

 narrowest part of the canal, being surrounded by fibres from the 

 retractor ani and Wilson's muscles ; it is sometimes called the 

 muscular division. The spongy portion extends from before the 

 ischial arch to the external opening, or meatus urinarius ; it is 

 narrow in the middle, but dilated at each end. The posterior 

 dilatation is known as the bulbous portion. Near the external 

 orifice the canal is contracted, but on reaching the glans it dilates 

 and forms the fossa navicularis. 



As the urethra leaves the neck of the bladder, there is an 

 elevation of its mucous membrane, called the uvula vesicae. On 

 laying open the urethra from the neck of the bladder, the first 

 object that attracts attention is an elongated ridge on the roof of 

 the prostatic portion, the caput gallinaginis, verumontanum, or 



Fig. 126. 

 Bladder and pelvic portion of urethra, seen from below — the latter being laid 

 open, a, Bulbous portion of vas deferens ; a'. Fold of peritoneum joining vasa 

 deferentia ; 6, Vesicula seminalis ; c, Right lobe of prostate gland ; d, Excretory 

 canals of prostate ; e, Cowper's gland of right side ; /, Its excretory orifices ; 

 g, Verumontanum with openings of ejaculatory ducts ; 7i, Opening of uterus 

 masculinus ; i, Bladder ; k, Orifices of ureters; I, Transverse section of corpus 

 cavernosum ; in, Transverse section of urethra. 



crest of the urethra, which contains the orifices of the ejaculatory 

 ducts and prostate vesicle ; and on each side of the crest is a 

 slight groove, the prostatic sinus, into which the prostatic 

 secretion is poured by numerous orifices. About the commence- 

 ment of the bulbous portion, just behind the membranous 

 division, are the openings of Cowper's glands. The urethral 

 mucous membrane is furnished with numerous depressions or 

 lacunee, which are receptacles of mucus. They are most plentiful 

 at the lower part of the spongy portion, and in the fossa navi- 

 cularis is a very large one, the lacuna magna. 



PENIS. 



The penis is the male organ of copulation ; it supports, or 

 rather contains, the greater part of the urethra. It may be said 



2 A 



