describe the idea of Jerome about the contended stomach

The narrator thinks this after having a nice supper at the Picnic Point, along with George and Harris. They all were very eager to have that meal and feel really contented after having it. It is this feeling of contentment that makes the author believe that one can feel immensely good and satisfied with himself and the world, only if he has a full stomach. For instance, before the supper, all three of them were quarrelsome and snappy and ill-tempered, but after they had a hearty meal, they sat and smiled at one another, feeling happy, contented and compassionate.

He feels that the digestive organs of a person dominate his intellect. He cannot work, cannot think, unless his stomach wants him to do so. It dictates to him his emotions and passions. As pointed out by him, after eggs, it is only the stomach that instructs the brain to work, after a thick slice of meat to sleep, after a cup of tea to rise and show strength, after hot muffins to be dull and soulless and after tonic to grin and enjoy.