MOVEMENTS OF THE SMALL INTESTINE. 379 



of the muscular coat of the intestine, its contents are passed 

 along, occasionally the action being reversed for a time, until 

 the indigestible residue, mixed with a certain quantity of 

 intestinal secretion, more or less modified, is discharged grad- 

 ually into the caput coli. These movements are apparently 

 not continuous, and depend somewhat upon the quantity of 

 matter contained in different parts of the intestinal tract. If 

 we are to judge from the movements in the inferior animals 

 after the abdomen has been opened, the intestines are con- 

 stantly changing their position, principally by the action of 

 their longitudinal muscular fibres, so that the force of gravity 

 does not oppose the onward passage of their contents as 

 much as if the relative position of the parts were constant. 

 There are no definite observations concerning the relative 

 activity of the peristaltic movements in different portions of 

 the intestine ; but from the fact that the jejunum is constant- 

 ly found empty, while the ileum contains a considerable 

 quantity of pultaceous matter, it would seem that the move- 

 ments must be more vigorous and effective in the upper por- 

 tions of the canal. 



The gases which are constantly found in the intestine 

 have, according to Longet, 1 an important mechanical func- 

 tion. They are useful, in the first place, in keeping the ca- 

 nal constantly distended to the proper extent, thus avoiding 

 the liability to disturbances in the circulation, and facilita- 

 ting the passage of the alimentary mass in obedience to the 

 peristaltic contractions. They also support the walls of the 

 intestine and protect these parts against concussions in walk- 

 ing, leaping, etc. The gases are useful, likewise, in offering 

 an elastic but resisting mass upon which the compressing ac- 

 tion of the abdominal muscles may be exerted in the acts of 

 straining and expiration. If we could suppose the intestinal 

 tube to be entirely free from gaseous contents, it is evident 

 that the functions above mentioned would be performed 

 imperfectly and with difficulty. 



1 LONGET, Traite de Physiologic, Paris, 1861, tome i., p. 152. 



