1432 



SUEFACE AND SUKGICAL ANATOMY. 



region, in the axis of the anal canal, until it reaches the cavity of the rectum, the inferior 

 part of which is dilated to form the ampulla. The transverse folds of the rectum or 

 valves of Houston, three in number, project into the cavity of the bowel in the form of 

 prominent crescentic shelves, which are produced by the three permanent or true flexures 

 into which the rectum ' is thrown (Birmingham) ; the inferior valve, which may be 

 sufficiently prominent to impede the passage of the finger, must not be mistaken for a 

 pathological condition. Through the anterior wall the finger can palpate from below up- 

 wards the bulb of the urethra, the membranous part of the urethra, the bulbo-urethral 

 glands (when inflamed and enlarged), the apex and lateral lobes of the prostate, the 

 vesiculas seminales, and the external trigone of the bladder. With the left forefinger in the 

 rectum, an instrument passed into the bladder can be distinctly felt as it traverses the mem- 



Posterior superior spine 



Upper lateral inflexio; 



Peritoneum (pararectal 

 fossa) 



Superior hsemorrhoidal 

 artery 



Rectum 



Sacro-tuberous ligament 

 Ischio-rectal fossa 



Anal canal 

 Anus 



Third sacral vertebra 



Fourth sacral vertebra 

 (cut) 



Inferior border of 

 piriformis (cut) 



Superior hsemorrhoidal 

 artery 



Lateral inflexion 

 Coccygeus 



Levator ani 



External sphincter 



FIG. 1108. THE RECTUM FROM BEHIND. 



The sacrum has been sawn across through the 4th sacral vertebra, and its inferior part removed with the coccyx. 

 The posterior portions of the coccygei, levatores ani, and of the external sphincter have been cut away. 

 The "pinching in " of the inferior end of the rectum by the medial edges of the levatores ani, resulting 

 in the formation of the flattened anal canal, is suggested in the illustration, which has been made from a 

 formalin-hardened male body, aged thirty. The lateral inflections of the rectum, corresponding to 

 Houston's rectal valves, are also shown. (From Birmingham.) 



branous urethra ; as it lies in the prostatic urethra it is separated from the finger by the 

 prostate. Hence, when a false passage is made through the bulbous or membranous portion of 

 the urethra, the instrument, if pushed onwards towards the bladder, will be felt immediately 

 outside the rectum between it and the prostate. In the child, owing to the rudimentary 

 condition of the prostate, the instrument is distinctly felt close to the rectum, as it lies in 

 the prostatic as well as in the membranous portion of the urethra. When the prostate is 

 not enlarged the tip of the finger can just reach the external trigone, which is most 

 distinctly felt when the bladder is full. The vesiculse seminales, indistinctly felt when 

 healthy, may be readily palpated when enlarged and indurated from disease. Through 

 the side wall of the rectum may be palpated the ischio-rectal fossa, the bony wall of the 

 pelvis minor, and, when enlarged, the hypogastric lymph glands ; through the posterior 

 wall the hollow "of the sacrum and coccyx, and the lymph glands lying in the retro- 

 rectal cellular tissue. 



