Toxic substances may include the following:

1. Products which are formed in the intestines due to normal metabolic reactions.Examples
   1. Foreign organic compounds which are not ordinarily ingested or taken once in a way.
   2. Drugs used for therapeutic purposes and chemicals used for therapeutic purposes.
2. Putrefaction: Products produced in the intestines through bacterial enzymatic reaction or normal digestion products.
3. Sex hormones or bile pigments which are normal physiological compounds and are eliminated to some extent as sulphate and glucuronide.