PERINEUM. 



923 



est deviation to either side brings the correspond- 

 ing vas deferens and vesicula seminalis into 

 peril. In the majority of full-grown subjects 

 the space under consideration is about three 

 inches distant from the anus, so as to permit 

 the index finger of the operator to reach it 

 without difficulty; but from statements already 

 made the reader will perceive that many excep- 

 tions to this rule may be encountered in prac- 

 tice. Again, the sides and base of this triangle 

 (so long as the neighbouring parts remain in 

 situ) are in general each of them respectively 

 less than one inch in length ; yet when the 

 bladder is removed from the subject and artifi- 

 cially distended, and when the connections of 

 the peritoneum are disturbed by dissection, the 

 space to which we refer becomes immensely 

 enlarged, and the anatomist is then apt to form 

 a most exaggerated and erroneous idea of its 

 natural dimensions. 



Against the recto-vesical paracentesis many 

 very serious objections may be raised. In 

 early life it should not be attempted, because 

 at that period the peritoneum descends so low, 

 and the under surface of the bladder is so little 

 developed, that injury to the serous membrane 

 of the abdomen would almost necessarily en- 

 sue. Even in the adult the great uncertainty 

 of the deptli of the peritoneal cul-de-sac, added 

 to the utter impossibility of ascertaining its 

 extent in the living subject, constitutes a weighty 

 argument against the operation ; whilst the 

 enlarged prostate (so very common in old men) 

 must frequently forbid its performance in after 

 life ; and the danger of wounding the vas 

 deferens or the vesicula seminalis, or of pro- 

 ducing urinary infiltration or a permanent fis- 

 tula, may be fairly urged against this mode of 

 relieving the bladder, at whatever age under- 

 taken. The other methods employed for the 

 same purpose in extreme cases of retention of 

 urine are also no doubt open to valid objec- 

 tions, but any further consideration of this 

 subject would be out of place in the present 

 article. 



In order to perform lithotomy successfully, 

 or to tap the bladder with safety, the surgeon 

 should ever bear in mind the direction of the 

 axis of that organ. In the adult male the axis 

 of the bladder runs nearly parallel to the axis 

 of the upper strait of the pelvis; but upon a 

 lower plane, that is to say, nearer to the pubis, 

 if produced, it would pass superiorly through 

 the linea alba between the umbilicus and the 

 pubis, and it would touch the inferior extre- 

 mity of the coccyx below. In the child its 

 direction is very variable, for the urinary reser- 

 voir being then in the abdomen and in contact 

 with the anterior "wall of that cavity, must 

 necessarily move in obedience to the abdominal 

 muscles, and every change of position which 

 the bladder undergoes exerts a marked influ- 

 ence upon its axis. During childhood the axis 

 of the bladder appears in the dead subject to run 

 from before backwards nearly horizontally, be- 

 cause the distended bladder, no longer sup- 

 ported by the abdominal muscles, turns for- 

 wards over the pubis; but in the living child, 



when the recti abdominis are forcibly con- 

 tracted, the line in question becomes nearly 

 vertical. 



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 

 degrees 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 isclna from a recent subject, with 

 the penis, the bladder, and the rectum attached ; 

 this can be easily accomplished by cutting the 

 horizontal ramus 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 

 many 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 ligament, 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 spongy 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- 



