VIII THE VOCAL AND RESPIRATORY ORGANS 



169 



movements may continue for quite a long period, especially 

 if the frog is kept quiet and where it is cool, without any 

 movements of the body or nares. During this time the 

 glottis remains closed and no air passes into or out of the 

 lungs. The nares are kept open, and air is drawn through 



O^Sf 



Fig. 46. — Diagrams to illustrate the respiratory movements of the frog. 

 In A the floor of the mouth is depressed, the nares are open, and air 

 rushes through them into the buccal cavity. In B the floor of the mouth 

 is raised, the nares are closed, and air is forced from the buccal cavity 

 into the lungs. ^.«, external nares ; ^/, glottis ; ^Zi?/, gullet ; z.«, internal 

 nares; Ing, lung; olf.s, olfactory chamber; pmx, premaxillary bone; 

 tng, tongue. (After Parker and Parker.) 



them into the buccal cavity as the floor of the mouth is 

 lowered, and forced out through them as the floor of the 

 mouth is raised. These oscillating movements perform two 

 functions : (i) they are subservient to the respiration which 

 takes place in the mucous walls of the mouth and pharynx, 

 and (2) by renovating the air discharged into the buccal 



