The diagram here introduced represents the calibre of the various bougies in general use, and the observer will perceive, that as they are made to accommodate themselves to the passage they have to pass, how varied must be the changes which the urethra undergoes. The last outline indicates the natural and healthy bore of the urethra. Bougies are manufactured of different materials: waxen cloth rolled together, elastic and yielding; flexible metal, silver, and gold. The bougies which I employ are constructed upon an improved plan to those in general use: the elastic, as they are termed, although assisted in their attempted passage to the bladder by the smooth and well-lubricated sides of the urethra, have a constant tendency to straighten, and consequently are liable to hitch in all the folds they may encounter, which, in relaxed habits, are very numerous in the membranous portion of the urethra. To obviate such a possibility, I prefer that the bougie should be of such a consistence and manufacture as will admit of its preserving the shape I adapt it to previously to introducing it; at the same time the material to be sufficiently soft to enable it to accommodate itself to any accidental tortuosity of the tube it is exploring. [Illustration] Catheters are instruments for the purposes of withdrawing the urine; they are consequently hollow, and are made of the same materials as bougies; but the most useful and to be depended upon are composed of silver. Surgeons, like other men, have their fancies: a catheter, when made of silver, has very little flexibility; accordingly it must be shaped beforehand. Some medical men prefer them quite straight, others with an immense curve. A surgeon should possess many forms, as the direction of the urethra differs almost in all men. The subjoined exhibits not the size, but the shape of the more useful and those most generally used. Figures 1, 2, and 3, suffice in most instances, whereas figure 4 is necessary in cases of enlargement of the prostate gland, which presses up the bladder, and renders the urethral passage consequently longer. [Illustration] The French employ not only variously curved instruments, but variously shaped. In peculiar cases they are doubtlessly useful; but they require to be used only by persons of skill and judgment. In the next three kinds are views of such; they are called conical bougies—the first curved, the second straight. They are made of silver, waxen cloth, or India-rubber. The third exhibits a sound, employed to ascertain the seat of the stricture.