the flow of urine
through the urethra happens occasionally to be suddenly arrested, and
this circumstance contrasted with the opposite fact that the organic
stricture is of slow formation, originated the idea that the former
occurrence arose from a spasmodic muscular contraction. By many this
spasm was supposed to be due to the urethra being itself muscular. By
others, it was demonstrated as being dependent upon the muscles which
surround the membranous part of the urethra, and which act upon this
part and constrict it. From my own observations I have formed the
settled opinion that the urethra itself is not muscular. And though, on
the one hand, I believe that this canal, per se, never causes by active
contraction the spasmodic form of stricture, I am far from supposing, on
the other, that all sudden arrests to the passage of urine through the
urethra are solely attributable to spasm of the muscles which embrace
this canal.

[Illustration]
Plate 58.--Figure 11.

COMMENTARY ON PLATES 59 & 60.

THE VARIOUS FORMS AND POSITIONS OF STRICTURES AND OTHER
OBSTRUCTIONS OF THE URETHRA.--FALSE PASSAGES.--ENLARGEMENTS
AND DEFORMITIES OF THE PROSTATE.

Impediments to the passage of the urine through the urethra may arise
from different causes, such as the impaction of a small calculus in the
canal, or any morbid growth (a polypus, &c.) being situated therein, or
from an abscess which, though forming externally to the urethra, may
press upon this tube so as either to obstruct it partially, by bending
one of its sides towards the other, or completely, by surrounding the
canal on all sides. These causes of obstruction may happen in any part
of the urethra, but there are two others (the prostatic and the
spasmodic) which are, owing to anatomical circumstances, necessarily
confined to the posterior two-thirds of the urethra. The portion of the
urethra surrounded by the prostate can alone be obstructed by this body
when it has become irregularly enlarged, while the spasmodic stricture
can only happen to the membranous portion of the urethra, and to an inch
or two of the canal anterior to the bulb, these being the parts which
are embraced by muscular structures. The urethra itself not being
muscular, cannot give rise to the spasmodic form of stricture. But that
kind of obstruction which is common to all parts of the urethra, and
which is dependent, as well upon the structures of which the canal is
uniformly composed, as upon t