ORIGIN OF LUNGS ng 



the fins and the muscular control of balance. Finally, 

 in a few catfish the gas chamber becomes connected 

 to the ear by a chain of little bones, in virtue of which 

 the perception of vibrations in the water is notably 

 enhanced. 



From some such appendages of the pharynx our 

 lungs are derived. Fish of different orders have 

 independently converted an outgrowth used at first 

 for temporary air-storage into a sac, round the walls 

 of which blood could be re-oxygenated and purified 

 of its carbon dioxide. The opening of this virtual 

 lung is even converted, in some fish, into a glottis or 

 voice-organ analogous to our own larynx ; and in the 

 so-called salmon (Ceratodus) of Queensland, once wide 

 spread over the northern hemisphere, the organ may 

 be spoken of as a pair of lungs, which exist side by side 

 with the gills ; it occupies the position and plays the 

 part of the lungs in ourselves, and, whilst useful at 

 all times, becomes of special respiratory value in foul 

 water or times of drought. 



The next stage in the evolution of our breathing 

 organs is traceable in the amphibious newts and frogs. 

 These have gills when young ; a little older they possess 

 both gills and lungs ; and in their adult stage lose 

 their gills and breathe mainly by lungs, reverting 

 at times of stress and subaqueous retirement to the 

 oldest known method of supplementing respiration, 

 namely, breathing through the skin. This power of 

 respiring air directly is associated with the conquest 

 of the land. As it is done through the nose, we find 



