THE URETHRA. 219 



The blood-vessels enclose the bladder with an arterial network within 

 the fibrous coat, from which twigs enter the muscular coat and break up into 

 capillaries, while others gain the submucous layer and form a network of the 

 larger stems; from this branches pass into the mucous membrane and give 

 rise to a rich capillary meshwork immediately beneath the epithelium. The 

 veins form a submucous plexus that drains the mucosa and empties into a 

 muscular plexus which, in turn, is tributary to the external subperitoneal 

 plexus. With the exception of the smaller ones on the inferior surface, the 

 vesical veins possess valves. The lymphatics begin as a close-meshed 

 plexus within the muscular coat, distinct lymph-channels being absent within 

 the mucous membrane. Outside the muscular coat they form a loose plexus 

 within the fibrous tissue (subperitoneal), the lymphatics from the apex and 

 body of the bladder coursing downwards and laterally and those from the 

 fundus upwards. 



The nerves include both spinal and sympathetic fibres, medullated and 

 nonmedullated, and within the fibrous coat are connected with ganglia, par- 

 ticularly in the vicinity of the ureters, from which twigs enter the muscular 

 coat and break up into smaller ones bearing microscopic ganglia. Other 

 branches gain the submucous layer, where they form plexiform enlarge- 

 ments, containing numerous groups of ganglion-cells; in addition to sympa- 

 thetic filaments to the blood-vessels, fine bundles of fibres proceed to the 

 mucous membrane to end in free terminations partly within the tunica 

 propria and, probably, to some extent between the epithelial cells. The 

 general sensibility of the normal bladder is comparatively slight, being 

 greatest in the trigonal region, especially at the ureteral openings. 



THE URETHRA. 



The urethra the canal through which the urine is conveyed from the 

 bladder to the exterior of the body differs in the two sexes, since in the 

 male, in addition to its common function of conducting the urine, it serves 

 for the escape of the secretions of the sexual glands." 



The Male Urethra. Considered with regard to the regions of the 

 body in which it lies, the male urethra may be divided into a pelvic, a peri- 

 neal and a penile portion. It is more usual, however, to describe the canal 

 as consisting of the prostatic, the membranous and the spongy portions a 

 division based on the anatomical relations to the structures through which 

 it passes. 



The wall of the urethra consists of a mucous membrane containing a 

 rich venous plexus and supplemented, in the prostatic and membranous 

 portions, by considerable tracts of muscular tissue. The tunica propria 

 possesses an unusual number of fine elastic fibres and is covered with an 

 epithelium that varies in different parts of the canal. Throughout the upper 

 two-thirds of the prostatic portion, the epithelium resembles that of the 

 bladder, being of the transitional variety; on approaching the membranous 

 portion, the epithelium becomes stratified columnar in type, small reserve 

 cells lying between the outer ends of the superficial elements, which are 

 often goblet-cells. Except within the beginning of the spongy portion (pars 

 cavernosa), where the lining is reduced to practically a single stratum of 

 cells, the columnar epithelium retains its stratified character as far as the 

 navicular fossa, the dilated distal end of the urethra. Here the epithelium 

 becomes stratified squamous and at the external urethral orifice is directly 

 continuous with the epidermis covering the glans penis. Within the 



