28 ANATOMY OF THE DOMESTIC FOWL 



and frontal, posteriorly with the temporal, and inferiorly with the 

 sphenoid, and palatine. 



Description. The ethmoid consists of a perpendicular and a 

 horizontal lamina. The perpendicular lamina, located between 

 the orbital cavities, is cajled the septum inter orbitale. On each side 

 of the septum interorbitale and near the superior orbital roof are 

 two foramina for the passage of the olfactory nerves. In the hori- 

 zontal plate, which forms the anterior cranial wall, are located the 

 optic foramina through which pass the optic nerves. 



FIG. 7. Side view of the skull of a hen. i, Lamina perpendicularis. 2, 

 Foramen for the. passage of the nerve of smell. 3, Foramen for the passage of 

 the optic nerve. 4, Nasal bone. 5, External nasal opening. 6, Premaxilla 

 7, Os dentale. 8, Superior maxilla. 9, Os jugal. 10, Os quadrato-jugal. n, 

 Os quadratus. 12, Pterygoideus. 13, Os articulare. 14, Inferior maxilla. 15, 

 Temporal. 16, External auditory canal. 17, Parietal. 18, Frontal. 19, Pala- 

 tine. 20, Orbital process, posterior to which is the processus zygomaticus. 



21, Interorbital foramen and optic foramen' for passage of optic nerve. 



22, Attachment for inferior oblique; 23, for superior oblique; 24, for levator 

 palpebrae superioris; 25, for internal rectus; 26, for superior rectus; 27, for external 

 rectus; 28, for inferior rectus; 28, for inferior rectus; 29, for depressor palpebrae 

 inferioris; 30, for orbicularjs palpebrarum; 31, for tensor tympani; 32, for circum- 

 concha. 



The Sphenoid. Location. The sphenoid, or os sphenoidale, 

 forms the floor of the cranial cavity and articulates with or touches 

 posteriorly the occipital, laterally the temporal, and anteriorly the 

 palatine, and ethmoid. 



Description. The sphenoid bone, the largest part of the cranial 

 floor, is formed by the fusion of the nasal and the cranial parts. It is 

 a three-cornered bone with two, thin, broad wings. These wings 

 are divided into two portions, orbital wings, or alee orbitales, and 



