BY W. J. McKAY. 911 



Os Pr^fkontale vel Anteorbitale, 



LachrymaU vel Frontale anterius, D' Alton ; Frontal anterieur, 

 Cuvier; Ethmoidale laterale vel prcfifroyitale, Gegenbaur, Harting, 

 Wiedersheim ; Prefrontale, Huxley ; Prcefrontale^ Hoffmann ; 

 Thrdnenhein, Meckel; Frontale anterius vel Orbitale anterius, 

 Job. Miiller, Owen ', Prcefrontale vel Ante-orhitale, Parker, Parker 

 and Bettany ', Frontale anterius vel Ethtnoideum, Stannius ; 

 Thrdnenhein, Rathke. 



The anterior orbital is an irregularly shaped bone resembling 

 somewhat the letter Z, being composed of two horizontal and one 

 vertical piece. 



The superior horizontal bar presents a superior surface flattened 

 internally, while externally there is a notch for articulation with 

 the projection of bone from the frontal. 



The notch is formed by an excavation which runs from above 

 downwards and outwards, at the same time extending more poste- 

 riorly below than above. The internal portion of the inferior 

 surface of the bone is flat, and gives attachment to the posterior 

 portion of the nasal capsule, while the external portion rests on 

 the pedicle of the bone. 



The pedicle is prismatic in outline, its axis running from above 

 downwards and outwards. The anterior surface is quadrilateral, 

 smooth, convex, and sub-cutaneous. The posterior surface smooth 

 with a large foramen at its lower edge, which leads to a canal 

 that opens on the inferior surface. This transmits the lachrymal 

 duct. This surface bounds the orbit anteriorly. 



The internal side of the prism is mainly composed of membrane, 

 so that a cavity is formed in the bone which is in relation with the 

 nasal canal close to the posterior nares. 



The inferior plate of bone is prismatic. The pedicle rests on 

 the internal half of its superior sides, while the outer half of the 

 plate helps to complete the anterolateral portion of the orbit. 



