Interpretation of the Appearances of the Small Pulmonary Blood Vessels in Animals

Abstract

A study was made of the histology of the small pulmonary blood vessels in uninflated postmortem specimens from the monkey, dog, fox, mouse, rat, rabbit, squirrel, sheep, pig, cow, seal, kitten, eivet, and guinea pig. The small pulmonary arteries appeared unusually muscular compared to those of man, and the increased medial thickness was reminiscent of the medial hypertrophy found as an early change in the human lung in diseases asso ciated with pulmonary arterial hypertension.This suggests to us that the histological cri teria usually employed for grade 1 hyperten sive pulmonary vascular disease in man are invalid when applied to lung biopsies from animals used for experiments on the pulmo nary circulation. There is a sphincter-like arrangement of the muscle of the media of the muscular pulmonary arteries of the guinea pig. In the rat, mouse, and squirrel there is an extension of cardiac muscle along the larger intrapulmonary veins. Fibromuscu Ear prominences project into the vein lumen iii the cow and the pig.