ALIMENTARY CANAL AND ITS APPENDAGES 237 



Fio. 189. — Diagrams of the Oral Cavity and Pharynx ok a Fisit (A), 

 Amphibian (B), Reptile or Bird (C), and Max (D). 



X, external nostril ; Ch, internal nostril ; D, alimentary canal ; K, gill-slits ; 

 L, lung ; T, trachea ; 0, a?sophagus : the arrow marked A indicates tlio 

 respiratory passage, that marked B the nutritive passage ; I , the point where 

 the two passages cross one another. 



