DEVELOPMENT OF SALIVARY GLANDS IN THE DOMESTIC CAT 209 



muscles of mastication; the palate process appears in the roof and 

 the buccal sulcus begins to be arched. The enlargement of the palate 

 process divides the mouth into a circumlingual and a marginal cavity, 

 meeting at the crest of the palate process in the alveohngual gutter. 

 As the tongue emerges by the fusion of its three anlages it becomes 

 defined against the alveohngual region by the lingual sulcus, which 

 appears first at its tip, then in the region of the submaxillary ganglion, 

 and last in the intennediate region. The lateral limit of the palate 

 process is defined by an ectopalatine sulcus, which serves to divide the 

 marginal cavity into an ental zone, the palatomandibular plane, 

 and an ectal, the ma.xillomandibular. Owing to the confinement of 

 the caudal portion of the mouth, the ma.xillomandibular plane is 

 here reduced to a solid fold, the orbital inclusion. This extends to 

 the orbital angle. The orbital angle marks the division of the marginal 

 cavity into a caudal postdental region, and a cranial dental portion, 

 which is characterized by the presence of the maxillomandibular plane 

 and the dental ridges. Caudad of the dental ridges the marginal 

 cavity narrows rapidly to the fauces, with which the circumhngual 

 space is broadly continuous. In subsequent development the circum- 

 hngual space, the alveohngual region, the palatomandibular plane, 

 and the maxillomandibular plane as far as the dental ridges are 

 allotted to the cavum oris proprius and the nasal fossae, only the 

 lateral portion of the maxillomandibular plane forms the vestibule. 

 Caudal of the dental ridges, which stop at the orbital angle, the ter- 

 minal portion of the palatomandibular plane forms the small post- 

 dental vestibule, communicating behind the teeth with the cavum oris 

 and rapidly narrowing to the fauces. 



The development of the sahvary apparatus begins caudad, in the 

 ontogenetically older portion of the cavity and proceeds craniad. 

 The glands of the cavum oris and vestibule form two distinct groups, 

 developing in the alveohngual region and maxillomandibular plane. 

 It will be convenient to follow their history in separate accounts. 



THE GLANDS OF THE VESTIBULE 



The glandiferous sulci are the buccal, the secondary buccal, and the 

 inferior alveobuccal, the last forming the ventral limit of the definitive 

 vestibule, and in front of the angulus oris intervening between the 



