

THE PEOSTATE. 



1431 



Anal canal 



FIG. 1107. THE INTERIOR OF THE ANAL CANAL AND INFERIOR PART 

 OF THE EECTUM. 



In the superior half of the anal canal are the rectal columns of Morgagni. Accord- 

 ing to Ball, fissure of the, anus is generally caused by the tearing downwards of one 

 of the posterior rectal sinuses (Fig. 1107) during the passage of a scybalous mass. 



According to Birmingham, the pubo-coccygeal fibres of the levator ani close the 

 superior parf of the anal canal, whilst the external sphincter closes the remaining 

 part. The internal 

 sphincter, according to 

 the same author, acts 

 probably as a detrusor, 

 its use being to empty 

 the anal canal completely 

 after the passage of the 

 faecal mass. 



Ischio-rectal Fossa. 

 The apex of the ischio- 

 rectal fossa (Fig. 1108), 

 formed by the attach- 

 ment of the inferior fascia 

 of the pelvic diaphragm 

 (anal fascia) to the ob- 

 turator portion of the 

 parietal pelvic fascia, is 

 directed up wards towards 

 the pelvis, and lies 2J in. 



from the Surface. The Showing the rectal columns of Morgagni and the rectal sinuses between their 

 medial Wall Of the fossa inferior ends. The columns were more numerous in this specimen 



,-, -i than usual. (From Birmingham.) 



is bounded by the levator 



ani and coccygeal muscles covered by the inferior fascia of the pelvic diaphragm 

 (Fig. 1108); the lateral wall by the obturator internus muscle covered by the 

 obturator fascia. An abscess in the ischio-rectal fossa should be opened early, other- 

 wise it is liable to burst through the medial wall into the rectum ; should it open 

 also upon the skin surface a complete "fistula in ano " is formed. When a " fistula 

 in ano " results from the bursting of a submucous abscess of the anal canal the 

 track of the fistula runs either medial to or through the fibres of the internal 

 and external sphincter muscles, and the external or skin opening is, as a rule, close 

 to the anus, while the internal opening is generally within the upper end of the 

 anal canal. Occasionally the ischio-rectal abscess perforates the levator ani towards 

 the apex of the fossa ; it then burrows into the peri-rectal cellular tissue of the 

 pelvis, and opens into the ampulla of the rectum. In other cases, again, the 

 abscess starts in the peri-rectal tissue internal to the levator ani, and either 

 bursts into the rectal ampulla or through the levator ani into the ischio-rectal 

 fossa, and so reaches the surface. Or the pus may burrow between the rectum and 

 coccyx, whence it may pass outwards through the greater sciatic foramen, behind 

 the parietal pelvic fascia, into the buttock ; or, by piercing the visceral layer of 

 the pelvic fascia, may reach the tela subserosa of fatty tissue of the pelvis and 

 ascend in it to form an iliac abscess. 



The lymph vessels from the skin of the anus pass along the perineo-femoral 

 folds to the most medial glands of the groin, both superficial and deep subinguinal. 

 According to Poirier and Cune*o, those from the region of the white line end in 

 the hypogastric glands which lie in front of the hypogastric artery, while those 

 which issue from the mucous membrane of the upper part of the anal canal 

 and the rectum proper traverse a few minute glands (ano-rectal glands of Gerota) 

 placed between the muscular and fibrous coats of the rectum, along the superior 

 hsemorrhoidal vein and its two branches, and pass thence to the sacral glands 

 which lie internal to the anterior sacral foramina. 



Digital Examination of Rectum. In making a rectal examination the finger 

 uld be carried forwards from the tip of the coccyx so as to enter the anus from behind, 

 finger is then gently pressed upwards and slightly forwards through the sphincteric 



91 c 



