It is well known that in certain portions of the canal relative in elasticity and limited dilatability are due to certain anatomical pecu liarities of the surrounding structures, e.g., at the opening in the triangular ligament, the junction of the fossa navicularis with the spongy urethra, the junction of the latter with the bulb, and at the meatus. At these various points the areolar tissue beneath the mucous membrane is scanty and the latter is more closely applied to the tissues upon which it rests. There is normally more strain at these points of narrowing than at any other portion of the canal, hence the urethra is here reinforced by an increased density of fibro connective tissue.
In explaining the localization of stricture, we will take as our point of departure the fact that the urethra is a dilatable tube, the elasticity of which varies at different points in the canal. Through this tube water at a certain pressure, and in a certain volume, is forced at more or less frequent intervals. Obviously the greatest friction is produced at the various points of normal contraction and relative inelasticity. Against the strain and friction produced at these points nature has provided a certain amount of reinforcement of tissue, and under normal circumstances, with a healthy mucous membrane, this pressure and friction do not produce injury. When, however, the canal is inflamed, its lumen and elasticity are decreased.
Urine is nevertheless pumped through the tube in as great a volume and with as great frequency as under normal circumstances, produc ing by its mechanical pressure, friction, and chemical effects consid erable irritation, as is evidenced by the consequent pain and smarting. Obviously, the greatest amount of irritation occurs at the points of relative inelasticity of the canal, and as a consequence it is here that inflammation tends to localize itself and persists, —perhaps long after the remainder of the mucous membrane has returned to a condition to a greater or less degree approximating the normal. This chronic inflammation results in a deposit of reparative material, which or ganizes and encroaches upon the lumen of the canal, forming, in short, organic stricture.
Regarding the relation of normal points of contraction to stricture, it may be said that such points of relative inelasticity and points of acquired contraction may be precisely the same from a clinical stand point in the presence of a pathological condition of the mucous mem brane. There is no difference in results, and there should be none in treatment, between a gleet perpetuated by normal points of fric tion and a similar discharge perpetuated by acquired contraction; the cure of the case demands their removal independently of their origin.