The mammalian lacteal: its histological structure in relation to its physiological properties

Abstract

The histological structure of the mesenteric lacteals of the guinea-pig, rat, cat, mouse, hedgehog, dog, pig, and squirrel is described. There is no histological evidence to show why the lacteals of the rat and guinea pig are contractile and those of the other species under the same conditions are not. It is pointed out how small an amount of smooth muscle is responsible for the rhythmic contraction in the rat and guinea-pig. The lacteals of the squirrel of less than 400 [mu] in diameter do not possess smooth muscle. They are, however, contractile to electrical and mechanical stimuli. These phenomena are adduced as additional evidence that some endothelial structures are contractile. The lacteals of the guinea-pig and squirrel have been shown to be innervated; the nerves are probably motor. Nerve cells have also been found on the vessels in the squirrel.