926 



PERINEUM. 



ing portion of the urethral canal, explain this 

 sufficiently ; nor should it be forgotten that the 

 muscular girth formed by the accelerators 

 urinae is often the seat of spasm. 



The error in catheterism of most frequent 

 occurrence here is the perforation of the floor 

 of the urethra at the bulb, after which the ex- 

 tremity of the instrument passes between the 

 rectum and the urethra. The surgeon commits 

 this mistake by neglecting to depress the handle 

 of the catheter in time to raise the point out of 

 the sinus of the bulb into the membranous 

 portion, and so much the more readily as the 

 slightest force exercised in this wrong direction 

 is sufficient to perforate the spongy tissue. 



The premature depression of the handle of 

 the catheter may likewise injure the urethra, 

 but in a different manner, for if that ma- 

 noeuvre be executed too soon and with undue 

 force, the point of the instrument will lacerate 

 the upper wall of the canal anterior to the tri- 

 angular ligament. 



A difficulty may, however, be experienced 

 in entering the membranous portion of the 

 urethra, even though the handle of the catheter 

 be depressed at the proper time ; the surgeon 

 in such cases fails to " hit off" the aperture in 

 the triangular ligament which transmits the 

 urethra, and the point of the instrument swerv- 

 ing laterally, comes to press against the front of 

 the triangular ligament at one side of the orifice, 

 instead of traversing the orifice itself. To guard 

 against such a casualty, care must be taken to 

 keep the point of the catheter fairly in the 

 middle line, and (should any obstruction arise) 

 to exercise slight traction upon the penis for the 

 purpose of rendering tense the fibrous covering 

 of the bulb, and in that manner stretching the 

 opening in the triangular ligament. 



From these principles it clearly follows that, 

 except under peculiar circumstances, curved 

 instruments are to be preferred, for their adapta- 

 tion to the curvature of the canal enables them 

 to reach the bladder without exercising undue 

 pressure upon any part of the passage ; whilst 

 the straight staff conducted ever so skilfully 

 must to a certain extent strain or disturb the 

 permanently curved portion of the urethra. 

 But, besides this obvious advantage, the natural 

 impediments to catheterism (placed chiefly 

 along the floor of the passage) are also most 

 easily surmounted by the curved instrument, 

 for its point can at any moment be readily 

 raised by the operator, whilst he accomplishes 

 the same object much more imperfectly in 

 using the straight staff. It cannot be denied, 

 however, that, for certain purposes, straight 

 instruments possess a decided superiority, and 

 therefore every surgeon should be prepared to 

 employ them when the occasion suits. 



The preceding outline describes with suffi- 

 cient accuracy the course and relations of the 

 principal organs belonging to the perineum, 

 and therefore it now only remains to study the 

 anatomy of this region from below, according to 

 the usual method of dissection. The subject is 

 of course supposed to be placed in the ordinary 

 position, with a full-sized staff introduced into 

 the bladder, the rectum artificially distended, 



the scrotum raised and drawn forwards, the 

 hands bound firmly to the ankles at each side 

 respectively, the pelvis elevated on a block, and 

 the knees separated to a convenient distance 

 from each other. 



Prepared in this manner, the perineum pre- 

 sents anteriorly a well-marked median promi- 

 nence corresponding to the urethra, and which 

 for obvious reasons enlarges considerably in 

 the living subject during erection. At either 

 side of this urethral prominence a parallel de- 

 pression exists, external to which the resisting 

 edges of the rami of the ischium and pubis may 

 be always readily recognised by the finger. At 

 the posterior part of the perineum the point of 

 the coccyx may be felt distinctly in the middle 

 line ; the tuberosities of the ischia covered by a 

 great depth of soft parts project remarkably at 

 the sides, constituting the extreme lateral limits 

 of the region, whilst the mid space between 

 these eminences exhibits a deep depression 

 containing the anus. In front of the anus a 

 central elevation of the skin termed the raphe 

 extends forwards along the perineum, and may 

 be traced distinctly to the scrotum and penis; 

 it serves as a guide to the surgeon in many 

 operations, pointing out the middle line accu- 

 rately so long as the integuments retain their 

 normal relations. 



Integument. The characters of the cuta- 

 neous covering of the perineum are not uniform 

 throughout ; in some situations its thickness is 

 very considerable, whilst in others it appears 

 remarkably delicate. In front the skin becomes 

 gradually finer as it approaches the scrotum, 

 and at the margins of the anus its delicacy is 

 extreme ; but in the neighbourhood of the 

 tuber ischii and along the edge of the gluteus 

 maximus it possesses great density and offers 

 considerable resistance to the scalpel : at the 

 circumference of the region it in fact gradually 

 assumes the properties of the neighbouring te- 

 gumentary membrane, resembling that of the 

 scrotum anteriorly, merging insensibly into the 

 integument of the buttock and thigh laterally, 

 and even approaching to the characters of mu- 

 cous membrane in the vicinity of the gut ; it is 

 generally of a dark brown colour in the healthy 

 adult, and of a lighter hue in the child ; but 

 there are in this respect numerous individual 

 varieties ; the darker the teint the more highly 

 developed usually are the subjacent muscles. 

 Cutaneous follicles abound in the perineum 

 and occur in greatest numbers near the anus and 

 at the root of the scrotum, where their secre- 

 tions are most required. The skin around the 

 anus is thrown into rugae disposed in a radiated 

 manner, and which produce a puckered appear- 

 ance so long as the orifice remains contracted : 

 they disappear during its dilatation, and are de- 

 signed to favour the extreme distension to which 

 the anal extremity of the intestine is occasion- 

 ally subjected during defecation. The folds in 

 question become at times the seat of fissure, 

 ulceration, or excrescence, which may demand 

 surgical interference for their relief. 



In the lateral operation of lithotomy the first 

 incision should commence at the left side of the 

 raphe, about an inch or an inch and a quarter 



