Investigation of Tracheal Respiration II: On Gaseous Diffusion in the Trachea
ARMY BIOLOGICAL LABS FREDERICK MD
Pagination or Media Count:
A formula is postulated for calculating, from the total cross-section and the average length of the tracheae of an insect, the differential pressure which is just sufficient to cover oxygen consumption by gaseous diffusion. Measurements of the tracheal systems of some large insect larvae show a differential pressure of about 2 and diffusion therefore is entirely sufficient to explain the transport of gas in the tracheae. Gas diffusion in the longitudinal tracheal trunks has been directly demonstrated in large larvae of Cossus and was measured the absence of actual respiratory motion was also demonstrated. It was demonstrated, by means of larvae of Aeschna, that the transport of gas is also exclusively supplied by diffusion alone in closed systems equipped with tracheal gills. In such forms, the tracheae must be capable of supporting high pressure without collapse in order to fulfill their function. The general significance of gaseous diffusion or tracheal respiration is discussed and the close relations between bodily size and efficiency of the respiratory mechanism by means of tracheae are demonstrated. For the smallest forms, diffusion is always adequate. For somewhat larger forms, it must be combined with mechanical respiration if the gaseous metabolism is intensive and even then there are rather narrow limits to possible size.
- Anatomy and Physiology