212 THE ENGINES OF THE HUMAN BODY 



strata in the caecum and colon as in the wall of the small 

 bowel, but they are arranged differently. The outer coat 

 is gathered into three bands which run along the colon 

 and pucker the fibres of the deeper lying circular stratum 

 into folds and pouches. That is because the movements 

 and transport system of the great bowel are profoundly 

 different from those of the small. Here there are no 

 peristaltic or "milking" waves. The lower part of the 



Fig. 44A. — The caecum covered by 

 its outer or peritoneal coat. 



Fig. 44B. — The caecum, appendix, and 

 ileo-caecal orifice laid open. 



small bowel fills the caecum in much the same way as 

 the oesophagus forces boluses of food into the stomach. 

 The caecum, and the same is true of the rest of the colon, 

 has a rhythmical contraction which gently and slowly 

 kneads the material within and is thus constantly bringing 

 its lining membrane into contact with fresh surfaces of its 

 contents. In order that the contents may be thoroughly 

 searched for every particle of digested food, the wall of 

 the colon is thrown into pouches and folds which are 

 ever changing their position and form, and thus coming 

 in contact with fresh material. One part of the great 



