THE MALE URETHRA. 1121 
A slight median elevation, which is continuous above with the crista urethree, 
projects into the canal from its posterior wall, and becoming less marked as it is 
traced downwards, is often seen to divide into two faint ridges. When the canal 
is empty other longitudinal folds or ridges are usually to be seen on the mucous 
membrane, but these become obliterated when the passage is distended. 
The terminal portion of the membranous urethra, where it is overlapped posteriorly by 
the urethral bulb, lies in front of the triangular ligament. It is considerably wider than 
the upper part of this subdivision of the canal, and is very thin-walled (Figs. 765 and 766). 
Spongy Portion of the Urethra—The third or spongy portion (pars 
cavernosa) of the urethra is much the longest of the three subdivisions. It begins 
at a point about half-an-inch in front of the posterior end of the bulb, and ends at 
the external orifice on the glans penis. — Its proximal portion has a fixed position 
and direction, while its distal part varies with the position of the penis. The canal 
is about six inches in length, and is surrounded throughout its whole extent by 
the erectile tissue of the corpus spongiosum and glans. Directed at first forwards 
through the bulb of the corpus spongiosum, the canal turns downwards and forwards 
at the point where it comes to lie in front of the lower part of the symphysis pubis 
(Fig. 766). This bend in the direction of the canal, roughly speaking, corresponds 
to the place of attachment of the suspensory ligament to the dorsum of the penis. 
When the penis is drawn upwards towards the front of the abdomen, the direction 
of the terminal half of the canal is of course changed, and at the same time the 
whole length of this subdivision of the urethra becomes more uniformly curved. 
The urethra as it enters the bulb lies at first in the upper part of the erectile tissue, 
but as it passes forwards it sinks deeper, and comes to occupy the middle part of the 
corpus spongiosum (Fig. 766). In the glans, on the other hand, most of the erectile 
tissue lies in the dorsal and lateral aspects of the urethra. Like the other parts of 
the urethra, the canal is closed except during the passage of fluid, the closure being 
effected by the apposition of the dorsal and ventral walls of the passage, except In 
the part of the canal which lies in the glans penis, where the lateral walls of the 
canal come into contact (Fig. 768). Thus the first part of the canal, when empty, is 
represented in cross section by a transverse slit, and the terminal part by a vertical 
sht. The spongy part of 
the urethra does not pre- 
sent a uniform calibre 
throughout, but is narrower 
- in its intermediate part, 
} where it traverses the 
corpus spongiosum, than it 
is in those portions of its 
course which are sur- 
rounded by the bulb and 
the glans. The terminal 
Maid |S 
Fic. 768.—A LONGITUDINAL SECTION OF THE TERMINAL PORTION OF THE 
dilated part of the passage PENIS, AND A TRANSVERSE SECTION THROUGH THE BoDY OF THE 
is termed the fossa navi- ORGAN. 
cularis urethre, and opens @ Corpus cavernosum. d. Glans penis. g. Dorsal vein. 
tl f: 7 the ver b. Corpus spongiosum. ¢. Fossa navicularis. h. Dorsal artery. 
on the suriace by tne ver- c. Urethral canal. /. Part of septum pectinifurme. 7. Dorsal nerve. 
tically-placed slit-like 
external urethral orifice (orificium urethre externum), which is bounded by lateral 
lips, and is the narrowest and least dilatable part of the whole urethral canal. 
The ducts of Cowper’s glands open by very minute apertures in the under 
wall of the proximal part of the spongy portion of the urethra. Before opening 
into the canal, they lie for some distance immediately beneath 1ts mucous mem- 
brane. A number of little pit-like recesses, called the lacune urethrales, also open 
into the spongy part of the urethra, and are so disposed that their openings lead 
obliquely into the canal in the direction of its external orifice. 
In some cases a somewhat valve-like fold of the mucous membrane is found in.the upper wall 
of the urethra in the region of the fossa navicularis. 
ial 
