THE URETHRA.- Anatomists describe the urethra as a canal presenting a double curva ture, of which the anterior segment is highly moveable, and of which the posterior is in a great measure fixed. The anterior segment (comprising the spongy portion of the urethra from the meatus urinarius to the vicinity of the bulb) exhibits, in the flaccid condition of the penis, a marked curvature concave downwards, which disappears, however, during erection, and which exerts little influence upon catheterism, since the surgeon easily obliterates it by raising the penis until it forms an angle of about forty deg,rees with the anterior wall of the abdomen. The posterior segment (consisting of the whole of the prostatic and membranous portions of the urethra, and also of the posterior part of its spongy portion) presents on the contrary a permanent curvature concave upwards, and belonging essentially to the perineum, it re quires in this place a special description. To dissect the perineal portion of the urethra with advantage, the anatomist ought to remove the greater part of the ossa pubis and the ascending rami of the ischia from a recent subject, with the penis, the bladder, and the rectum attached ; this can be easily accomplished by cutting the horizontal mmus of the pubis at each side perpendicularly with a saw as near the aceta bulum as possible, after which the instrument may be made to traverse the foramen ovale, and divide the ramus of the ischium in the immediate vicinity of its tuberosity. If the bladder be then inflated from one of the ureters, and the rectum distended, the preparation will exhibit in a satisfactory manner the urethra and rnany other parts described in this article, of which but an imperfect view is obtained in the ordinary dissection of the perineum from below.
The posterior segment of the urethra repre sents a reversed arch, of which the centre lies about ten lines beneath the symphysis pubis, whilst the extremities incline upwards, the one in front and the other behind the symphysis. Ample provisions exist to render this arch per manent; its centre, constituted by the mem branous portion of the urethra, is transmitted through the triangular lig,ament, and adheres by its circumference to the edges of the opening through which it passes; its posterior extre mity, formed by the prostatic urethra, is tied up to the back of the pubis by the anterior true ligaments of the bladder, whilst the true sus pensory ligament of the penis in front, and the prolonged attachments of the crura penis, pin ning that organ up to the anterior surface of the pubis, raise the spong-y portion of the urethra at its commencement, and consequently elevate the anterior extremity of the arch. The per manency of this arch depends of course mainly upon the strength and resistance of the afore said ligaments; yet, although the properties of these structures are well known to anatomists, a difference of opinion prevails as to the pos sibility of rendering the urethra stmight by simple traction of the penis.
The true suspensory ligament is calculated by its position and strength to prevent the surgeon front depressing the penis sufficiently to straighten the urethra, and in the dead sub ject no force so applied, short of what suffices to tear the ligament in question and to rupture partially the attachment of the crum penis to the bones, can efface the curvature of the pos terior segment of the canal, but if the suspen sory ligament be divided by the knife, and if at the same time the crum penis be detached ever so little from the pubis, the slightest trac tion exercised subsequently upon the penis renders the urethra perfectly straight. The writer by no means intends to deny that cathe terism by straight instruments is a feasible operation : to straighten the urethm by drawing the penis in certain directions, and without any other aid, is one thing, and to introduce a straight instrument into the bladder along the urethra is a totally different matter ; to accom plish the former, either in the living or the dead subject, so long as the true suspensory ligament is uninjured and the crum penis re tain their attachments, will be found absolutely impossible, whilst the latter operation may very genemlly be performed by any surgeon who possesses ordinary dexterity. The princi ple on which the introduction of straight in struments is effected admits of ready explana tion. 13y raising the penis as before described the operator renders the urethra, from the glans to the bulb inclusive, perfectly straight, and therefore the staff traverses the passage so far without impediment, but any attempt to force it farther in the same direction would rupture the lower wall of the urethra, and pro pel the point of the instrument towards the rectum. The hinder portion of the canal leads upwards and backwards to the bladder, and it therefore remains to be explained how a straight instrument, occupying the spongy part of the urethra, and with its point directed downwards and backwards towards the rectum, can have its course so changed as to pass upwards and backwards to the bladder. The solution of the problem is easy: the handle of the instrument is first dmwn forwards so as to furm a right angle with the pubis, and then depressed until it becomes nearly parallel with the patient's thighs, whilst at the same time an onward rnovement is communicated to it, whereby the point glides upwards and backwards into the bladder. In these movements the staff ob viously represents a lever of the first order, the fulcrum formed by the lower wall of the ure thra opposite to the true suspensory ligament of the penis, and the beak of the instrument being elevated as its handle is depressed.