134 A MANUAL OF ANATOMY 



maxilla, the upper teeth slightly overlap the lower. According to 

 the degree of projection of the maxillary bones, skulls are spoken 

 of as orthognathous, prognathous, or mesognathous. 



The chief small foramina of the anterior region are as follows, 

 from above downwards at either side : supra-orbital, at the junction 

 of the outer two-thirds and inner third of the supra-orbital arch 

 of the frontal (which in most cases is a notch) ; infra- orbital, in the 

 superior maxilla near the infra-orbital margin ; mental, in the 

 inferior maxilla in line with the septum between the bicuspid 

 alveoli ; and malar, situated above the malar tuberosity. The 

 supra-orbital, infra-orbital, and mental foramina are in the same 

 perpendicular line, and transmit the following important sensory 

 nerves, in order from above downwards : supra-orbital, infra- 

 orbital, and mental, which are branches of the ophthalmic, 

 superior maxillary, and inferior maxillary divisions of the Gasserian 

 ganglion on the sensory root of the fifth cranial nerve. The malar 

 foramen transmits the malar branch of the temporo-malar or 

 orbital nerve, from the superior maxillary division of the fifth. 



The sutures in the anterior region are as follows : fronto-malar, 

 fronto-maxillary, lachrymo-maxillary, fronto-nasal, internasal, naso- 

 maxillary, malo-maxillary, and intermaxillary. 



The Orbits. — The orbits have the shape of four-sided pyramids, 

 their bases being directed forwards and outwards, and their apices 

 backwards and inwards. The inner walls are nearly parallel, and 

 occupy an antero-posterior plane, but the outer walls diverge, the 

 plane of each being directed forwards and outwards, so that they 

 almost fo:m a right angle with each other. Each orbit is lined 

 with periosteum, which is continuous with the dura mater through 

 the sphenoidal fissure, and it contains the eyeball, with the ocular 

 muscles, nerves, and bloodvessels, the lachrymal gland, and a large 

 amount of fat. It presents an apex, a base, and four sides or 

 walls. The apex, which is directed backwards and inwards, is 

 formed by the inner end of the sphenoidal fissure, and just above 

 and internal to this is the optic foramen. The base is free, and 

 is directed forwards and outwards. Its circumference presents the 

 fronto-malar suture externally, the malo-maxillary inferiorly, and 

 the fronto-maxillary internally. The walls are superior, inferior, 

 external, and internal. 



The superior wall or roof, which is thin and brittle, is formed 

 mainly by the orbital plate of the frontal, and behind this by the 

 small wing of the sphenoid. It is smooth and concave. Within 

 the external angular process it p esents the lachrymal fossa lor 

 the lachrymal gland, and near the internal angular process the 

 trochlear fossa, which gives attachment to the cartilaginous pulley 

 of the superior oblique muscle of the eyeball. 



The inferior wall or floor is fo med by three bones, namely, the 

 orbital surface (orbital plate) of the superior maxilla, external to 

 which is a part of the orbital process of the malar, whilst posteriorly 

 is the orbital process of the palate bone. The floor is thin, and sepa- 



