PERINEUM. 



921 



losing altogether its cylindrical shape. It will 

 be readily understood that when such a dispo- 

 sition prevails in a calculous subject, the rectum 

 must undergo serious danger during lithotomy 

 performed according to the lateral or bilateral 

 methods, and that therefore the precaution of 

 emptying the bowel previous to these opera- 

 tions is highly advisable. 



The relations of the perineal portion of the 

 rectum deserve from the surgical anatomist his 

 most attentive consideration. Anteriorly the 

 inferior fundus of the bladder, together with 

 the vesiculee semmales and vasa deferentia, 

 come into contact with the rectum immediately 

 beneath the line of reflection of the peritoneum ; 

 lower down the prostate gland rests upon the 

 front of the rectum, to which it is very inti- 

 mately connected, nothing but some cellular 

 tissue intervening between them, whilst still 

 lower down the membranous portion of the 

 urethra and the bulb are related to the rectum, 

 though not immediately, for neither of those 

 parts of the urinary apparatus is found to touch 

 the parietes of the gut. The bulb of the urethra 

 in the adult is usually situated about half an 

 inch in front of the rectum and about one 

 incli above the anus ; the membranous portion 

 of the urethra lies about ten lines anterior to 

 the rectum, and rather more than an inch and 

 a half above the anus, whilst the prostate gland 

 is placed within one line of the anterior wall of 

 the gut, and about two inches above the anus. 

 These anterior relations of the rectum explain 

 how the finger introduced into its cavity may 

 assist the catheter in its passage along the 

 urethra in the living subject; how by the same 

 manoeuvre the surgeon obtains valuable infor- 

 mation as to the state of the bladder and pros- 

 tate gland in various morbid conditions of those 

 organs ; how, in sounding, he is able at times 

 to raise up the calculus by his finger so as to 

 bring it into contact with the instrument; how 

 the bladder may be punctured from the rectum 

 and the urine withdrawn by this route in certain 

 cases of retention ; how, acute inflammations 

 and other diseases of the bladder and urethra 

 or their appendages so frequently occasion mor- 

 bid sympathies in the intestine, such as pro- 

 lapsus, tenesmus, hemorrhoids, &c. ; and above 

 all, how great must be the danger to the bowel, 

 and how urgent the necessity for protecting it 

 during the lateral operation of lithotomy. 



Posteriorly a quantity of loose cellular tissue 

 connects the lower part of the rectum to the 

 sacrum and coccyx; it is there related, parti- 

 cularly when distended, to the pyriformis and 

 ischio-coccygeus muscles, and towards its anal 

 extremity to some of the fibres of the levatores 

 ani and the ano-coccygeal ligament. 



On either side the rectum gives insertion to 

 a portion of the reclo-vesical layer of the pelvic 

 fascia, which, though weak and cellular in that 

 locality, nevertheless admits of being fairly 

 traced to the walls of the gut ; but the levatores 

 ani muscles constitute the principal lateral rela- 

 tions of the intestine. In their descent they 

 cover its surface extensively, and form in great 

 measure the partition between the bowel and 

 the ischio-rectal fossa;. 



The perineal portion of the rectum affords in 

 some respects a striking contrast to the upper 

 part of the same intestine; being totally devoid 

 of serous investment, it is more fixed and 

 (except at the anus) more dilatable than the 

 superior division of the bowel, and its con- 

 nexions with the recto-vesical layer of the pelvic 

 fascia, the ano-coccygeal ligament, the genito- 

 urinary passages, and the middle tendinous 

 point of the perineum, contribute to fix it still 

 more firmly in its position. 



The coats of the rectum present certain pecu- 

 liarities interesting to the surgical anatomist. 

 Its muscular tunic is of uncommon strength, 

 and consists of two very distinct layers ana- 

 logous in many particulars to those of the 

 corresponding strata in the oesophagus; the 

 superficial layer is formed of highly developed 

 longitudinal fibres, florid in colour (as con- 

 trasted with those of the remainder of the large 

 intestine), and which spread out so as to invest 

 the whole circumference of the gut: the fibres 

 of the deeper layer are circular, and acquire 

 increased developement towards the anal extre- 

 mity of the intestine, where they are continuous 

 with the internal sphincter. The mucous mem- 

 brane is remarkable for its thickness and vascu- 

 larity and for the great laxity of its connexion 

 with the other tissues of the gut: it adheres so 

 loosely to the subjacent coat in the vicinity of 

 the anus that it sometimes protrudes through 

 that opening, and in this manner one form of 

 prolapsus ani is produced. 



Upon the free surface of the mucous mem- 

 brane a number of longitudinal folds run down 

 to the immediate neighbourhood of the anus ; 

 they are called the columns of the rectum, and 

 converge slightly as they descend ; their number 

 is variable though it seldom exceeds eight or 

 ten, and between them inferiorly some trans- 

 verse semilunar folds may be observed, of whicli 

 the free concave margins are directed upwards. 

 In these folds of the mucous membrane the 

 physiologist recognises a provision to facilitate 

 the distension of the gut, and to their presence 

 some surgeons attribute the occurrence of cer- 

 tain morbid conditions of the intestine. In 

 addition to these folds, which are constant, 

 others have likewise been described within the 

 rectum ; these latter were named by the late 

 Dr. Houston " the valves of the rectum," and 

 appear at times remarkably distinct. When 

 present they are each of a semilunar shape, 

 and formed by a duplicature of mucous mem- 

 brane containing cellular tissue and a few 

 muscular fibres between its folds. Each valve 

 is attached by its convex margin to the walls of 

 the gut, whilst its free edge is directed more or 

 less inwards towards the cavity of the intestine. 

 One of these valves is situated (according to 

 Houston's statement) opposite to the base of 

 the bladder, on the anterior wall of the gut and 

 about three inches distant from the anus, whilst 

 another is sometimes placed within one inch of 

 the anal orifice. 



That projections from the parietes of the 

 rectum, such as have been described by Houston, 

 may be made apparent by a certain mode of 

 preparation cannot be denied, but that they can 



