INTERIOR OF THE URETHRA. 413 



I can readily measure its length by passing a probe into it, and on 

 opening it, it will be found that its blind extremity is somewhat 

 dilated. Along its wall, on each side, is placed the common seminal and by its 

 duct (/), which terminates on or within the margin of the mouth ejacifiatory 

 of the sac ; and if bristles are introduced into the common seminal ducts. 

 duct behind the prostate, they will render the apertures evident. 

 Small glands open on the surface of the mucous membrane lining 

 the utricle, which is the remains of the united lower ends of the 

 foetal ducts of Muller, and represents the uterus and vagina in the 

 female. 



On each side of the central crest is an excavation, which is named Prostatic 

 the prostatic sinus (fig. 154, /). Into this hollow the greater num- i n floor, 

 ber of the ducts of the prostatic glands open ; but the apertures of 

 some are seen at the back of the central eminence. 



The MEMBRANOUS PART OF THE URETHRA (fig. 154, g) IS three- Membran- 



quarters of an inch in length, and intervenes between the apex of ous P art: 

 the prostate gland and the bulb (&) of the corpus spongiosum 

 urethra?. In its interior are slight longitudinal folds. This is the dimensions ; 

 narrowest piece of the whole tube, with the exception of the outer 

 orifice, and measures rather less than a quarter of an inch across. 

 It is the weakest of the three portions of the canal, and is supported parts 

 by a thin stratum of erectile tissue, by a thin layer of unstriated aroundi 

 circular fibres, and outside all by the constrictor urethra muscle. 



The SPONGY PART (fig. 154, i) reaches to the end of the penis. Spongy 

 It is about six inches in length, and its strength depends upon a par ' 

 surrounding material named the corpus spongiosum ure three. 



The average size of the canal is about a quarter of an inch in dimensions ; 

 diameter, though at the vertical slit (meatus urinarius), by which 

 it terminates on the glans penis, the tube is smaller than elsewhere. 

 On a cross section it appears star-shaped, but in the glans as a 

 vertical slit. Two dilatations exist in the spongy portion ; one is two diiata- 

 along the floor close to the triangular ligament, being contained in on^inlraib 

 the bulb or bulbous part of the urethra, and is named the sinus oy one in glans; 

 the bulb ; the other is an elongated hollow, situate in the glans 

 penis, and is called the, fossa navicularis (n). 



There are many small pouches or lacunae (o) in the canal as far lacunae, 

 back as the membranous part, which have their apertures turned 

 towards the outer orifice of the urethra. One of these, larger than one larger 

 the rest, lacuna magna, is found generally immediately within the re ^ 

 meatus, in the roof of the fossa navicularis. 



The ducts of Cowper's glands (fig. 154, h) are two in number, Ducts of 

 and terminate, one on each side, on the floor of the urethra near the cowper? 

 bulb ; but their openings are generally too small to be recognised. 



Mucous lining of the urethra. The mucous membrane of the Mucous 

 urethra is continued into the bladder, as well as into the ducts membrane; 

 opening into the canal, and joins in front the tegumentary covering 

 of the glans penis. It is of a reddish colour in the spongy and colour; 

 membranous portions, but in the prostate it becomes whiter. In 

 the spongy and membranous parts it is thrown into longitudinal folds; 

 folds during the contracted state of the penis. 



