32 ANATOMY OF THE DOMESTIC FOWL 



into the nose. This bone is the base of the upper portion of the 

 beak and determines its form. It forms the anterior walls of 

 the nasal cavity. It has between the nasal bones, two processes 

 which extend back to the anterior point of the cerebral cavity. 

 The posterior part of the incisivum and nasale are flat, thin, and 

 elastic. The extensions then are the processus maxillaris, the 

 processus palatinus, and the processus frontalis, the first of which 

 forms part of the jaw rim, the second, which aids in forming the 

 gum plate, and the last which reaches to the anterior portion of the 

 cranial wall. 



The Maxilla. Location. The superior maxillaries, or ossa maxil- 

 lares, two in number, form the floor of the upper beak, a part of 

 the palatine roof and nasal walls. 



Each maxilla borders laterally the premaxilla and the nasal; 

 inferiofly, the anterior point of the palatine; and posteriorly, the 

 jugale. 



Description. The maxillae are thin, flat, bones. They have 

 three borders and three angles. The palatine processes of the two 

 bones do not meet in the median line, which results in a cleft in 

 the median palatine region. The bone-like gums are formed partly 

 by the palatine processes but more largely by lateral wings of the 

 os incisivum. Each maxilla has posteriorly a yoke-like extension, 

 superiorly a small extension, and also a palatine process. The 

 latter articulates by a facet with the vomer 



The Nasal. Location. The nasal bones, or ossa nasalia, two 

 in number, are located in the lateral facial region. The nasal bone 

 articulates posteriorly with the frontal; laterally, on the inner 

 border, with the processus frontalis of the premaxilla, and on the 

 outer border with the lacrimal; and inferiorly with the premaxilla, 

 maxilla, jugale, and vomer. 



Description. The nasal bone, or os nasale, is broad, flat, and 

 elastic and forms the posterior wall of the nasal opening. Under 

 this bone is located the infraorbital sinus. 



There are three extensions: first, the processus intermaxillaris, 

 which forms the upper wall of the nasal cavity; second, the processus 

 maxillaris anterior, directed downward and forward, which fuses 

 with the maxillary bone and forms the posterior rim of the nasal 

 cavity; and third, a posterior processus frontalis, which lies parallel 

 with the ethmoid. 



The Lacrimal. Location. The lacrimal bones, or ossa lacrimalia, 



