Lungs Amphibian lungs 

The lungs of most frogs & other amphibians are simple balloon-like structures, with gas exchange limited to the outer surface area of the lung. This is not a very efficient arrangement, but amphibians have low metabolic demands & also frequently supplement their oxygen supply by diffusion across the moist outer skin of their bodies. Unlike mammals, which use a breathing body system driven by negative pressure, amphibians employ positive pressure. The majority of salamander species are lungless salamanders, which respirate through their skin & tissues lining their mouth. The only other known lungless tetrapods are also amphibians the Bornean Flat-headed Frog & Atretochoana eiselti, a caecilian.

The lungs of amphibians typically have a few narrow septa of soft tissue around the outer walls, increasing the respiratory surface area & giving the lung a honey-comb appearance. In some salamanders even these are lacking, & the lung has a smooth wall. In caecilians, as in snakes, only the right lung attains any size or development.