DIGESTION AND METABOLISM 23 



the intestine is most acid, pH 6-49, the gizzard being at 6-72 and 

 the rear intestine pH 7-32. The range here is almost a pH unit. 

 Each region of the ahmentary canal carries its own distinctive 

 protozoan population. Kagawa (1949) reports pH values of 6-99 

 for the rear end of the gut and 7-4 in the oesophagus and anterior 

 intestine in Pheretima communissima and P. divergens. 



Summary 



Oligochaetes are mainly omnivorous, but often selective in their 

 food sources. Enzymes reported in the gut include lichenase, 

 protease, cellulase, chitinase, amylase and lipase. These enzymes 

 break down the components of the food ingested and mobilize it for 

 use by the animal. The occurrence of a cellulase, apparently 

 produced by the intestinal wall of Liimhriciis, is particularly interest- 

 ing since many animals feeding on plant material rely on intestinal 

 flora and fauna to hydrolyse cellulose. An invertase enzyme has 

 been mentioned as occurring in worm casts. The enzymes of the 

 gut have distinctive pH optima but the gut contents are remarkably 

 stable with regard to pH since it apparently varies only between 

 about pH 6-3-7-3 along its length. 



