INCOME OF MATTER 95 



of the walls it is thoroughly mixed with 

 the contents. The action of pepsin is on 

 proteins, converting these into a more special- 

 ized form of protein, termed peptone ; and 

 in this action it is assisted by the free hydro- 

 chloric acid of the gastric juice. The juice, 

 by acting on the walls of the cells in the food 

 stuffs, liberates fatty matters, or granules of 

 more or less cooked starch, and thus these are 

 prepared for further digestion. Saline matters, 

 that may have escaped the solvent action of 

 the saliva, are dissolved. Protein food stuffs, 

 as in cooked butcher meat, are disintegrated 

 into fibres and small morsels; these are 

 then acted on by the pepsin and hydro- 

 chloric acid. The result is the formation of 

 a semi-digested mass, the chyme, which, as it 

 is formed, escapes through the pyloric opening 

 into the first portion of the small intestine, the 

 duodenum. During the digestive process in 

 the stomach, the orifices at the lower end of the 

 oesophagus and at the beginning of the small 

 intestine, the pyloric opening, are tightly 

 closed by sphincters. Thus a portion of any 

 protein in the food is converted into simpler 



