ALIMENTARY CANAL AND ITS APPENDAGES 237 



o 



Fio. 189, DIAGRAMS OF THE ORAL CAVITY AND PHARYNX OF A FISH (A), 

 AMPHIBIAN (B), REPTILE OR BIRD (C), AND MAN (D). 



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

 L, lung; T, trachea; O, oesophagus: the arrow marked A indicates the 

 respiratory passage, that marked R the nutritive passage ; f, the point where 

 the two passages cross one another. 



