W8 



THE DISSECTION OF PIG EMBRYOS 



point in the median line where the lateral and median palatine processes meet, 

 fusion is not complete, leaving the incisive fossa, and laterad between the two 



Median palatine 

 process 

 Lateral palatine 

 process 

 Internal choancs 



Oral cavity 



Median palatine 

 process 



Raphe of lateral ^ 

 palatine process ^ 



Nasal passa 

 Anlage of uvula 



A B 



Fig. 152. — Dissections to show the development of the hard palate in pig embryos. X 5. A, 

 Ventral view of palatine processes of a 22 mm. pig embryo, the mandible having been removed; B, Same 

 of 35 mm. embryo showing fusion of palatine processes. 



processes openings persist for some time, which are known as the incisive canals 

 (of Stenson). 



In human embryos these changes are essentially identical (Fig. 153). The 

 lateral palatine processes begin to fuse cranio-caudaUy at about the end of the 



p.^.' p.g. 



mii 



Fig. 153. — The roof of the mouth of a human embryo about two and a half months old, showing 

 the development of the palate (after His). X 9. p.g., Processus globularis; p.g.', palatine process 

 of processus globularis; mx, maxillary process; mx', palatine fold of maxillary process. Close to the 

 angle between this and the palatine process of the processus globularis on each side are the prim- 

 itive choanae. 



second month. At the same time palatine hones first appear in the lateral pala- 

 tine folds and thus form the hard palate. Caudally the bones do not develop 



