296 DIGESTION. 



containing a large quantity of cholesterine, which disappears from the evacuations when 

 the digestive function becomes established. 



Movements of the Large Intestine. 



Movements of the general character which we have noted in the small intestine occur 

 in the large intestine, although the peculiarities in the arrangement of the muscular fibres 

 and the more solid consistence of the contents render these movements in the large in- 

 testine somewhat distinctive. In all instances where the movements have been observed 

 in the human subject or in the lower animals, they have been found to be less vigorous and 

 rapid than the contractions of the small intestine. Indeed, when the abdominal organs 

 are exposed, either in a living animal or immediately after death, movements of the large 

 intestine are generally not observed, except on the application of mechanical or galvanic 

 irritation ; and they are then more circumscribed and are much less marked than in any 

 other part of the alimentary canal. In the rabbit, in which the colon is very large, the 

 few spontaneous movements which are sometimes seen on opening the abdomen immedi- 

 ately after death are feeble and irregular, particularly in the caecum. That the fa3ces re- 

 main for a considerable time in some of the sacculated pouches of the colon, is evident 

 from the appearance which they sometimes present of having been moulded to the shape 

 of the canal. This appearance is frequently observed in the dejections, which are then 

 said to be u figured." 



In the caecum, the pressure of matters received from the ileum forces the mass onward 

 into the ascending colon, and the contractions of its muscular fibres are undoubtedly 

 slight and inefficient. Once in the colon, it is easy to see how the contractions of the 

 muscular structure (the longitudinal bands shortening the canal, and the transverse fibres 

 contracting below and relaxing above) are capable of passing the faecal mass slowly 

 onward. Although the transverse fibres are thin and seemingly of little power, their con- 

 traction is undoubtedly sufficient to empty the sacculi, when assisted by the movements of 

 the longitudinal fibres, especially as the canal is never completely filled and the fasces are 

 frequently in the form of small, moulded lumps. By these slow and gradual movements, 

 the contents of the large intestine are passed toward the sigmoid flexure of the colon, 

 where they are arrested until the period arrives for their final discharge. The time 

 occupied in the passage of the fseces through the ascending, transverse, and descending 

 colon is undoubtedly variable in different persons, as we find great variations in the inter- 

 vals between the acts of defecation. During their passage along the colon, the contents 

 of the canal assume more and more of the normal fecal consistence and odor and become 

 slightly coated with the mucous secretion of the parts. 



It has been pretty conclusively shown that the accumulation of fseces generally takes 

 place in the sigmoid flexure of the colon ; for, under normal conditions, the rectum is found 

 empty and contracted. This part of the colon is much more movable than other por- 

 tions and is better calculated as a receptacle for fseces. At certain tolerably regular in- 

 tervals, the faecal matter is passed into the rectum and is then almost immediately dis- 

 charged from the body. 



Defalcation. 



In health, expulsion of faecal 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 

 defascation ; and sometimes, in cases of irregularity, physicians have recommended pa- 

 tients to make an effort to void the fseces at a certain time every day, this practice being 

 frequently followed by the best results. At the time when defecation ordinarily takes 

 place, a peculiar sensation is experienced calling for an evacuation of the bowels ; and, 

 if this be disregarded, the desire may pass away, after a little time, the act becoming 



