9(52 MALE ORGANS OF GENERATION. 



and muscular tissue, and it has been supposed that this eminence, when dis- 

 tended with blood, may offer an obstacle to the passage of the semen back- 

 wards into the bladder. (E. H. Weber, Zusatze zur Lehre vom Baue und 

 Vcrrichtungen der Geschlechts-Organe, 1846 ; Huschke in Scemmerriug's 

 Anatomie, vol. v. ; Leuckart, " Vesicula Prostutica," in Cyclop, of Anat. & 

 Phys.) 



2. The membranous portion of the urethra comprises the part between 

 the apex of the prostate, and the bulb of the corpus spongiosum. It mea- 

 sures three quarters of an inch along its anterior, but only about half an 

 inch on its posterior surface, in consequence of the projection upwards on it 

 of the bulb. This is the narrowest division of the urethra. In the middle 

 its circumference is O'G of an inch ; at the end 0'5. (H. Thompson.) It is 

 placed beneath the pubic arch, the anterior concave surface being distant 

 nearly an inch from the bone, leaving an interval, occupied by the dorsal 

 vessels and nerves of the penis, by areolar tissue, and some muscular fibres. 

 Its lower convex surface is turned towards the perinseutn, opposite to the 

 point of meeting of the transverse muscles : it is separated by an interval 

 from the last part of the rectum. About a line in front of the prostate, it 

 emerges from between the anterior borders of the levatores ani, and passes 

 through the deep layer of the subpubic fascia (p. 260) ; it is then placed 

 between that and the anterior layer or triangular ligament through which 

 it passes some way farther forwards, but both of these fibrous membranes 

 are prolonged upon the canal, the one backwards and the other forwards. 

 Between these two layers the urethra is surrounded by a little erectile tissue, 

 by some veins, and also by the fibres of the compressor urethrce muscle ; 

 beneath it, on each side, are Cowper's glands. The proper or plain muscular 

 fibres of this portion of the urethra are continued over the outer and inner 

 surfaces of the prostate into the muscular coat of the bladder posteriorly, 

 and into those of the spongy portion of the urethra anteriorly. (Hancock.) 



3. The sponciy portion of the urethra, by far the longest and most vari- 

 able in length and direction, includes the remainder of the canal, or that 

 part which is surrounded by the erectile tissue of the corpus spongiosum. 

 Its length is about six inches. The part contained within the bulb, some- 

 times distinguished as the bulbous portion, is somewhat dilated ; its circum- 

 ference being equal to seven-tenths of an inch (Thompson). The succeeding 

 portion, as far as the glans, is of uniform size, being intermediate in this 

 respect between the bulbous and membranous portions. The cross section 

 of its canal appears like a transverse slit. The canal of the urethra situated 

 in the glans has, on the contrary, when seen in a cross section, the form of 

 a vertical slit : in this part the canal is again considerably dilated, forming 

 what is named the fossa navicularis, which is from four to six lines in length, 

 and is most evident in the form of a depression on the floor of the urethra. 



Lastly, at its orifice, which is a vertical fissure from two and a half to 

 three lines in extent, and bounded by two small lips, the urethra is again 

 contracted and reaches its narrowest dimensions. In consequence of its 

 form, and also of the resistant nature of the tissues at its margin, this open- 

 ing does not admit so large an instrument as even the membranous portion 

 of the canal. 



The mucous membrane of the urethra possesses a lining of stratified 

 epithelium, of which the superficial cells are columnar, except for a short 

 distance from the orifice, where they are squamous, and where the subjacent 

 membrane exhibits papillae. 



The whole lining membrane of the urethra is beset with small mucous 



