Foreword

The stomach and intestines are not only given to humans for the consumption of food and drink; they also form a comprehensive, well-structured, multi-layered precursor of our organism in its self-assertion against the disease-causing influences of the environment. The entire digestive tract essentially houses an inner external world that penetrates through our body, exposing it to countless mechanical, chemical, and microbial stimuli and influences, against which it must differentiate and defend itself. The structure, cellular, and biochemical functions of the gastrointestinal tract are ingeniously designed to cope with the constant distinction between foreign and self, between what is useful, essential for life, and what is harmful, destructive, that penetrates through it—a masterpiece of nature. Evolved over millions of years, the symbiosis, the togetherness, has also emerged.