The increasing importance of the relief topography of the mucosa in the refinement of gastro-intestinal roentgenography is well recognized. The constitution of the elements of the relief topography has been made the subject of an exhaustive morphologic and experimental investigation by Stenn Grettve at the Karoline Institute in Stockholm. He has made a comprehensive survey of the literature of the past hundred years and places special emphasis on the work of Forssell, who emphasized the plasticity of the mucosa and the lack of preformed anatomic folds.
Grettve demonstrates that the thickening of the muscularis mucosae at the height of a fold is an active process of contraction. The mucosal capacity for enlargement in response to intraluminal changes in pressure includes the ability of the low relief to alter its surface. Thus when the stomach is full the crypts are widened and flattened, and it is possible to see the openings