DEVELOPMENT OF THE DIGESTIVE TUBE 



615 



Fig. 289. Palatal conditions in frog, chick, and mammal. (A) Frog, adult. (B) 

 Chick, 16-day embryo. (C) Human adult. (Redrawn and modified from Morris, 1942, 

 Human Anatomy, Blakiston, Phila.) Only the anterior or hard palate is supported by 

 bone, the soft palate being a fleshy continuation of the palate caudally toward the 

 pharyngeal area. (D-F) Stages in development of the palate in the pig. (D) 20.5 mm. 

 (E) 26.5 mm. (F) 29.5 mm. 



is formed between the root of the tooth and the walls of the alveolar 

 socket, is called a gomphosis (fig. 286E). 



The permanent teeth, which supplant the deciduous teeth, develop in much 

 the same manner as the deciduous teeth. Man, Uke the majority of mammals, 

 develops two sets of teeth and, consequently, is diphyodont. Some mammals, 

 such as the mole, Scalopus, never cut the permanent teeth, while the guinea 

 pig sheds its deciduous teeth in utero. 



5) Formation of the Secondary Palate. In the fishes and the amphibia, a 

 secondary palate, separating the oral cavity from an upper respiratory passage- 

 way, is not formed. The formation of a secondary palate begins in the turtle 

 group and is well developed in the crocodilians and mammals. The bird also 



