As the title indicates, this is indeed a curious history of the gut or, more accurately, the digestive system as a whole.
Throughout history, the sounds, odors, emanations, effluents, and eventually the entrails of the system have all been used to predict and /or explain health or disease. At present, it is the microscopic inhabitants of the gut that are of much interest.
While the purpose of the book - to explain these various uses - is admirable, the length of time devoted to each use is excessive.