THE ACCEl 



vening septum they are rarely symmetrical. The following are their average 

 measurements: vertical height, 2.2 cm.; transverse breadth, 2 cm.; antero-posterior 

 depth, 2.2 cm. When exceptionally large they may extend into the roots of the 



Ethmoidal infundibulum 

 Ant. ethmoidal air cells 



Primitive frontal sinus 

 i Nasolacrimal duct 



pterygoid processes or great wings, and may invade the basilar part of the occipital 

 bone. Each sinus communicates with the sphenoethmoidal recess by means of 

 an aperture in the upper part of its anterior wall. They are present as minute 

 -cavities at birth, but their main development takes place after puberty. 



Ant. ethmoidal air cells 4 

 Post, eihmoidal air 



Gasserian ganglion 



Optic foramen 

 Int. carotid art. 

 Oculomotor nerve 

 Trochlear nerve 



Frontul sinus developing 

 from a frontal cell 



hmoidal infundibulum 

 >8sa of lacrimul sac 



laxillary ostium 



Abducens nerve 

 Int. carotid art. 



FIG. 861. Specimen from a child one year, four months, and seven days old. Lateral view of frontal, 

 ethmoidal, and maxillary sinus areas. (Davis.) 



The Maxillary Sinus (sinus maxillaris; antrum of Highmore), the largest of the 

 accessory sinuses of the nose, is a pyramidal cavity in the body of the maxilla. 

 Its base is formed by the lateral wall of the nasal cavity, and its apex extends into 

 the zygomatic process. Its roof or orbital wall is frequently ridged by the infra- 



1 Davis, W. B. Nasal Accessory Sinuses in Man, 1914. 



