396 PRACTICAL ANATOMY. 



laris, an expanded portion of the canal. The meatus 

 is the smallest part of the urethra ; it is a vertical, slit- 

 like opening, which becomes elliptical when distended 

 by the passing column of water. It is about one-quarter 

 of an inch long, and is bounded laterally by two slightly- 

 developed labia, joined by delicate commissures. 



The mucous membrane of the urethra is continuous 

 with that of the bladder, and externally with that of the 

 glans. In the non-distended state the spongy and mem- 

 branous urethra is thrown into longitudinal folds, and a 

 section exhibits the urethra as a transverse slit, with its 

 walls in contact. In the glans penis the flaccid urethra 

 is a vertical slit. The entire urethral mucous membrane 

 is studded with minute, tubular, mucous glands, known 

 as the glands of Littre. One of these glands, called the 

 lacuna magna on account of its size, is situated on the 

 upper wall of the fossa navicularis. The epithelium is 

 squamous and transitional, and columnar in the fol- 

 licles and ducts. The muscular coat of the urethra con- 

 sists of two layers, an outer longitudinal and an inner 

 circular. Their use is to expel the last drops of urine 

 evacuated from the bladder into the urethra ; they prob- 

 ably also assist in the ejaculation of the semen. 



THE PROSTATE GLAND. 



The prostate gland surrounds the neck of the bladder. 

 It resembles a horse-chestnut in size and form, and is 

 placed behind the symphysis pubis, and rests on the ante- 

 rior wall of the rectum. Its broadened base surrounds the 

 neck of the bladder. Its apex encroaches on the mem- 

 branous urethra. It weighs about half an ounce ; is 

 about one inch long, one and one-quarter inches broad, 

 and three-fourths of an inch thick, and consists of two 

 large, symmetrical, lateral lobes and a small central lobe. 



