John Harvey Kellogg 
Itinerary of a Breakfast [PDF ebook] 
A Popular Account of the Travels of a Breakfast Through the Food Tube and of the Ten Gates and Several Stations Through Which It Passes, Also of the Obstacles Which It Sometimes Meets

The artificial conditions of civilized life, sedentary habits, concentrated foodstuffs, false modesty, ignorance and neglect of bodily needs, have produced a crippled state of the colon as an almost universal condition among civilized men and women. Intestinal toxemia or autointoxication is the most universal of all maladies, and the source of autointoxication is the colon with its seething mass of putrefying food residues.