80 THE SKULL AS A WHOLE. 



Periotics ; Greater parts of the petrous and mastoid portions of the temporal bones. 

 Basisphenoid ; Posterior part of the body of the sphenoid bone, including the sella 

 turcica. 



Alisphenoids ; Great wings of the sphenoid with the external pterygoid plates. 

 Fresphenoid ; Anterior part of the body of the sphenoid bone. 

 Orbitosphenoids ; Small wings of the sphenoid bone. 



2. MEMBRANE -BONES COMPLETING THE CRANIAL WALL. 



Interparietal ; Tipper division of the tabular part of the occipital bone. 



Parietals ; The parietal bones. 



Frontals ; United in the single frontal. 



Squamosals ; The squamous parts of the temporal bones with the zygoma. 



3. BONES DEVELOPED IN THE CARTILAGINOUS NASAL CAPSULE. 



Mesethmoid ; Vertical plate of the ethmoid bone, together with the cartilaginous part of 

 the nasal septum. 



Ethmoturbinals ; The lateral masses of the ethmoid, including the upper and lower 

 turbinate bones. 



Maxilloturbinals ; The inferior turbinate bones. 



Sphenoidal turbinals ; The sphenoidal spongy bones. 



4. MEMBRANE-BONES DEVELOPED AROUND THE NASAL CAPSULE AND FORMING 

 THE GREATER PART OP THE UPPER FACE. 



Lachrymals ; The lachrymal bones. 



Nasals ; The nasal bones. 



Maxillae ; The superior maxillary bones, excepting the incisor part. 



Premaxillse or intermaxillae ; The incisor parts of the superior maxillary bones. 



Jugrals or malars ; The malar bones. 



Palatals ; The palate bones. 



Pterygroids ; The internal pterygoid plates. 



Vomer ; The vomer. 



6. BONES DEVELOPED IN THE CARTILAGINOUS VISCERAL ARCHES OF 



THE HEAD. 



Malleus, Incus, and Stapes ; The auditory ossicles or malleus, incus, and stapes. 

 Tympanohyals and Stylohyals ; The styloid processes of the temporal bones. 

 Epihyals ; The stylo-hyoid ligaments (occasionally ossified in man). 

 Ceratohyals ; The small cornua of the hyoid bone. 

 Thyrohyals ; The great cornua of the hyoid bone. 

 Basihyal ; The body of the hyoid bone. 



6. MEMBRANE-BONES DEVELOPED IN CONNECTION WITH THE VISCERAL ARCHES. 



Mandible ; The inferior maxillary bone (a small part is developed in the cartilaginous 

 arch). 



Tympanics; The tympanic plate, forming the auditory and vaginal processes (developed in 

 the periphery of the membrane closing the first visceral cleft). 



The relations of the nerves at their passage out of the cranium to the osseous elements 

 are remarkably constant, and afford considerable assistance in determining their homologies. 

 Thus, the nerves of the principal sense-organs pass into their special capsules as follows, viz., 

 the olfactory between the mesethmoid and ethmoturbinal divisions of the ethmoid bone ; the 

 optic between the orbitosphenoid and the presphenoid ; and" the auditory between the prootic 

 and opisthotic divisions of the periotic mass. Farther, the motor nerves of the orbital muscles 

 (third, fourth and sixth), together with the ophthalmic division of the trifacial (fifth), pass 

 through the sphenoidal fissure between the orbitosphenoid and alisphenoid, while the second 

 division of the trifacial has a special foramen in the alisphenoid which has been separated off 

 from the sphenoidal fissure by the growth of bone around the nerve. Similarly, the foramen 

 ovale for the third division of the trifacial has been cut off from the foramen lacerum between 

 the alisphenoid and periotic. The facial (seventh) nerve leaves the cranial cavity with the 

 auditory between the divisions of the periotic, and then traverses a canal (aqueduct of 

 Fallopius), the lower part of which is included between the outer surface of the periotic and 



