DIGESTION IN THE INTESTINE 171 



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From cystin and cystein, hydrogen sulphide and mercaptans 

 are produced. 



Many of the products of bacterial action are not harmful. It 

 is even possible that bacteria may in some ways be of service to 

 the organism, as in attacking and breaking down indigestible 

 substances, and producing from them materials which can be 

 utilized by the body. In putrefaction, however, many harmful 

 substances are produced, as above stated, and are responsible 

 for the well-known ill effects of constipation. The material 

 retained in the intestine putrefies, the products are absorbed 

 into the blood, and give rise to headaches and various other 

 symptoms causing discomfort. 



Putrefaction is greatly favored by an alkaline reaction. Also 

 most of the harmful substances resulting from putrefaction 

 come from the proteins. Limiting the amount of protein in the 

 diet and thoroughly chewing the food so that it may be digested 

 quickly will greatly reduce putrefaction in the intestine. 



Feces. In every mixed meal there is some material which is 

 indigestible and will not be attacked by the digestive enzymes. 

 Connective tissue, cellulose, etc., are examples of such sub- 

 stances. This material remains in the intestine and forms a 

 part of the solid excreta, or feces. In addition, the feces con- 

 tain enormous numbers of dead bacteria. Between one half and 

 one fourth of the solid matter of the feces consists of dead bac- 

 teria. The feces also contain the waste material of the cells of 

 the intestinal mucosa. and the residues of the digestive secre- 

 tions. The total amount of solids excreted in the feces per day 



