406 DIGESTION. 



other portions, and is better calculated as a receptacle for 

 faeces. 1 At certain tolerably regular intervals, the faecal 

 matter is passed into the rectum and is then almost imme- 

 diately discharged from the body. 



Defecation. 



In health, expulsion of fsecal matters takes place with 

 regularity generally once in the twenty-four hours. This 

 rule, however, is by no means invariable, and dejections may 

 habitually occur twice in the day, or every second or third 

 day, within the limits of perfect health. It is well known 

 that habit has a great influence upon the regularity of defe- 

 cation; and sometimes, in cases of irregularity, physicians 

 have recommended patients to make an effort to void the 

 faeces at a certain time every day, this practice being fre- 

 quently followed by the best results. At the time when def- 

 ecation ordinarily takes place, a peculiar sensation is experi- 

 enced calling for an evacuation of the bowels ; and if this be 

 disregarded, the desire may pass away, and after a little time, 

 the act becomes impossible. Under these circumstances, it is 

 probable that the faeces are passed out of the rectum by anti- 

 peristaltic action. 



The condition which immediately precedes the desire for 

 defecation is probably the descent of the contents of the 

 sigmoid flexure of the colon into the rectum. It was formerly 

 thought that the faeces constantly accumulated in the dilated 

 portion of the rectum, where they remained until an evac- 

 uation took place ; but the arguments of O'Beirne against 

 such a view are conclusive. He has demonstrated by numer- 

 ous explorations in the human subject, that under ordinary 

 conditions, the rectum is contracted, and contains neither 

 faeces nor gas. It is, indeed, a fact familiar to every surgeon 

 that the rectum usually contains nothing which can be 

 reached by the finger in physical examinations, and that 



1 O'BEIRNE, New Views of the Process of Defecation, Washington, 1834, 

 pp. 11, 12. 



