DEFECATION. 407 



paralysis or section of the muscles which close the anus by 

 no means involves, necessarily, a constant passage of faecal 

 matter. O'Beirne not only found the rectum empty and 

 presenting a certain amount of resistance to the passage 

 of injected fluids, but on passing a stomach-tube into the 

 bowel, after penetrating from six to eight inches, it passed 

 into a space in which its extremity could be moved with 

 great freedom, and there was instantly a rush of flatus, of 

 fluid fasces, or of both, through the tube. In some instances in 

 which nothing escaped through the tube, the instrument con- 

 veyed to the hand an impression of having entered a solid 

 mass ; and on being withdrawn contained solid faeces in its 

 upper portion. 1 According to this observer, the sensation 

 which leads to an effort to discharge the faeces is produced by 

 the accumulation of matters in the sigmoid flexure, which 

 finally present at the contracted portion of the rectum just at 

 its commencement. This constriction, situated at the most 

 superior portion of the rectum, is sometimes spoken of as the 

 sphincter of O'Beirne. 



The above is undoubtedly the mechanism of the descent 

 of faecal matter into the rectum in defecation, as the act is 

 usually performed ; but under certain circumstances, faeces 

 must accumulate in the dilated portion of the rectum. Ordi- 

 narily, the discharge of faeces only takes place after the efforts 

 have been continued for a certain time ; and when the evacua- 

 tion is " figured," the whole length discharged frequently ex- 

 ceeds so much the length of the rectum, that it is evident that a 

 portion of it must have come from the colon. O'Beirne states, 

 indeed, that he has frequently examined the rectum at the 

 moment when a moderate inclination to go to stool is felt, and 

 found it empty and contracted. 2 But in cases where the faeces 



1 O'BEIRNE, op. cit., p. 12. 



2 O'Beirne apparently fails to make a sufficiently accurate distinction between 

 "a moderate inclination to goto stool" (Op. cit., p. 12) and the peculiar sensation 

 which seems to demand a prompt evacuation. This latter we beh'eve to be due to 

 the presence of faecal matter in the rectum. 



