THE ORBITAL CAVITY. 



47 



the ophthalmic, with its three branches, and the nerves supplying the ocular muscles the oculo- 

 motor, the trochlear, and the abducent. All these nerves, except the optic, enter the orbit through 



Nasal cavity 



Eyeball- 



M. rectus 



interims 



M. rectus 



externus 



Dura) sheath of 



optic nerve 



M. temporalis 



Optic nerve flj 



Internal carotid 



artery 



Optic chiasm 



Oculomotor 



nerve 



Cerebral 

 peduncle" 



Aqurcductus- 

 cerebri 

 Corpora 

 quadrigemina 



Straight sinus - 



Cut surface of 

 falx cerebri 



Superior longi- 

 tudinal sinus 



Occipital bone 

 Scalp 



Dorsum nasi 



Septum nasi 

 cartilagineum 



Zygomatic pro- 

 cess 



-~ 1; "-* Ethmoidal cells 



Periorbita 

 Great wing of 

 sphenoid bone 



Sphenoid sinus 



Squamous por- 

 tion of temporal 

 bone 



FIG. 17. A horizontal section of the head in the plane of the palpebral fissures (frozen section). The plane of 

 section passes through the orbits in such a way as to show the entire length of the optic nerves as well as a portion of 

 the optic chiasm. The cerebellum lies in the posterior cerebral fossa and is covered in by the tentorium cerebelli, which 

 has been left intact. In the incisura tentorii may be seen the cross-sections of the two cerebral peduncles; the entire 

 cerebrum has been removed. 



