76 BOXES OF THE HEAD. 



belonging to the principal organs of the senses pass into their sense capsules as 

 follows, viz.: a, the olfactory through the cribrifonn plate developed in connection 

 with the ethmo-tuvbiiial ; h, the optic through the inner part of the orbito-sjihe- 

 noid ; c, the auditory dii-ectly into tlie periotic ; th the motor nerves of the eye- 

 ball and its muscles, with the ophthalmic division of the trifacial, between the 

 oi'bito-sphenoid and ali-spheuoid ; e, the second and third divisions of the trifacial 

 through the mner part of the ali-sphenoid ; /, the facial by its descending division 

 through the meatus internus. the so-called aqueduct of Fallopius and the stylo- 

 mastoid foramen, and by the Vidian nerve, tlu-ough the pterygoid foramen : f/, 

 the glosso-pharpigeal. pneumogastric, and spinal-accessory nerves between the 

 petrosal and exoccipital ; and the hjiwglossal nerve through the condylar fora- 

 men of the exoccipital. The intenaal carotid artery, it may be fui-ther stated, 

 enters the cranium by a canal separated from the foramen lacei-um medium or 

 spac® between the petrous, basi-occipital, and basi-sphenoid ; and the jugular vein 

 issues by the fore part of the foramen lacerum posterius. 



A general review of the relations of the bones of the head leads to the conclu- 

 sion that they may be looked upon as consisting mainly of three sets of parts, 

 viz.: 1st, Basal or central parts, forming a series prolonged foi-wards in the 

 Ime of the vertebral axis, and constituting a cranio-facial axis : 2nd, Lateral 

 superior arches, enclosing the brain or much-expanded medullary centre ; and 

 ord, Lateral inferior arches, enclosmg, in jiart at least, the visceral cavity as 

 represented by the nose, mouth, and pharynx. Together with the foregoing 

 are associated two other sets of elements, viz., 1st, the Sense capsules or 

 cavities, which are inteiposed between other bones, and are connected with the 

 lodgmtiut of tlie higher organs of sense, the nose, eye, and ear : and in the 

 case of the nose, but more especially of the ear. the capsules arc formed of 

 special and complex l)ony apparatus ; and 2nd, Superadded or investingr bones, 

 which are extraneous to the more fundamental osseous elements. 



Vertebrate theory of the skull. — It is mainly this relation of a superior 

 neural arch and an inferior visceral arch to parts of the skull which are central 

 or basicranial, notwithstanding the great expansion of the one and the limited 

 nature of the other, which has made it a favourite view of many anatomists to 

 comiDare the plan of construction of the skull to that of a series of vertebrae, 

 from the time when the idea of a vertebrate theory of the skull first occurred to 

 Goethe in 17'J1, and was subsequently, though independently, conceived and 

 worked out by Oken, and first iniblished Ijy him in 1807. This theory, however, 

 has un lergone various modifications in the hands of the successive comparative 

 anatomists by whom it has been supported ; while others of distmction have 

 refused to admit the validity of the grounds on which it has been framed. More 

 recent researches, and especially those of W. K. Parker, have thro'wn much new 

 light on the subject. 



The osseous segments which have hitherto been most frequently regarded by 

 anatomists as representing central vertebral elements iir the head correspond with 

 the four basicranial bones distinguished in the preceding table, viz., the occipital, 

 basisphenoid, pre-siihenoid, and mesethmoid ; the vomer being merely an investment 

 of the last. The upper or neural arches connected respectively with these as 

 centra are as follows, viz.. with the first or basioccipital. the exoccipital and 

 supraoccipital surrounding the foramen magnum, and in which few refuse to 

 recognise something of the vertebral character ; 2nd. with the basisplienoid, the 

 _alisphenoid and parietal, to which the temporal seems also to contribute a part : 

 ;}rd, with the i^resphenoid. the orbito-sphenoid and frontal ; and 4th. with the 

 mesethmoid, also the frontal and the nasal, if the latter bone be included in the 

 number of superior arches. The lower or" visceral arches are less easily referred 

 to their respective centra. But if, leaving aside the more precise detennination 

 of their morphological relations which may residt from a full study of embryo- 

 logy, we regard cliiefly their fonn and connections after the bones have attained 

 their osseous condition, the following elements may be enumerated in an order 

 from before backwards, uicluding the investing or superimposed bones along 

 with those of the arches, viz. : 1st, the preraaxillar}'^ ; 2nd. the i^terygo-maxil- 

 lary. including the palate ; :!rd, the mandiliular. including the cai-tilage 

 of Meckel and the malleus ; 4th, the upper or cerato-hyoid, mcluding the incus 



