Thoracic collapse as affected by the retia thoracica in the dolphin

The carcass of a subadult female Delphinus was placed in a hyperbaric chamber and subjected to two simulated dives each equivalent to 69.7 m. In one dive the thorax was in its natural state, and in the other 100 ml of water had been injected into each pleural cavity. Various morphometric measurements of the thorax were taken before, during, and after each dive. Results indicate that if fluid is located in the same position as the retia thoracica, the shape of the thorax is affected when submitted to diving, but not surface, pressures. The overall collapse of the chest is greater during partial infusion of the pleura, exhibiting exceptional compression in the ventral area. The engorged thoracic rete apparently affects the degree and pattern of thoracic collapse and thereby reduces the amount of displacement stress exerted upon the abdominal organs when the animal is subjected to the high ambient hydrostatic pressures encountered during normal diving.