Morphological Studies of the Mucous Membrane of the Small Intestine of Vertebrates with an Emphasis on Comparative Anatomy
In order to explicate the morphological and adaptive variations occurring in the mucous membrane of the small intestine, a morphological study was conducted from a phylogenetic viewpoint of the small intestinal mucosa of fish, amphibians, reptiles, birds and mammals, including man. A tendency for the mucosa to have gradually changed from that of folds only to that of fine villi as evolution proceeded was noted. It was further noted that as the evolutionary scale is climbed, there is a tendency for both the columnar cells, which make up the epithelium, and the microvilli observed at their apices to become shorter. Another interesting discovery was that the basal lamina of the mucosal epithelium of fish living near the delta of rivers is multi-layered and has a unique wavelike laminar structure.