DEVELOPMENT OF THE SKULL IN THE PIG. 



305 



the membranous cranium ; here we shall see the " recurrent laminyc" (i'c.c.) on each side 

 of the vomer (v.), and a still nearer approach of the edges of the under palatal floor. 

 The tenth section (fig. 10) is through the most projecting part of the hemispheres, but 

 in front of the olfactory crus ; here, above the inferior turbinal, folds of cartilage are 

 appearing in the roof, the foremost part of the upper turbinal {u.tb.). Plere the septum, 

 now to be called the perpendicular ethmoid [p.e.], is at its highest, and we are now 

 behind the recurrent processes of cartilage. At this part the palatal bands meet each 

 other, and in them a new bony centre has appeared, the maxillary (mx.j).) ; like the 

 premaxillary, it begins below. The next section (fig. 11) is through the widening 

 ethmoidal region and the partly separated olfactory crura (1), as well as through the 

 hemispheres (C 1"). The twelfth section (fig. 12) is through the cavity of the hemisphere, 

 which is being cut off from that of the olfactory crus (1) : it is immediately in front of 

 the eye, the anterior (inner) canthus being cut through. This section is of great 

 interest ; here we are behind the aliethmoidal cartilages above, and the olfactory bulbs 

 rest upon the soft mat through which their fibres root down into the nasal cavity. 

 The walls, both outer and middle, reach further backward than the roof of the nasal 

 sac ; and in tlie middle wall we see the ribbed condition caused by thickening at the 

 junction of the trabecular crests with the double keel sent down by the nasal alaj. 

 Here the middle turbinal arises above the inturned nasal wall which ends the inferior 

 turbinal (m.tb., i.th.). This section is behind the new maxillary centre, but shows a 

 large tooth-rudiment on each side of the conjugating palatal flaps; the antagonist teeth 

 appear in rudiment below on each side of the severed tongue [tg.), above the growing- 

 den tary (f/.), whilst inside the dentary is the Meckelian rod (mk.). 



The next section (fig. 13) is through the anterior third of the eyeballs (e.) and the 

 middle of the hemispheres (C 1"), and behind the perpendicular ethmoid; here the rest 

 of the septum is almost, if not entirely, of trabecular origin ; the section is in front of 

 the junction of the orbito-sphenoidal cartilages (o.. 5.) with the basal median part. But 

 if the mesoethmoid is dying out here, the nasal wall (n.tu.) continues much further 

 backward, bordering the greater part of the so-called presphenoid (p-5.). We are 

 now behind the upper and lower turbinal regions, and here the " middle turbinal " 

 (m.tb.) is near its extremity ; one interspace is cut through. This narrow, subcranial, 

 presphenoidal part of the nasal labyrinth, running so far backwards parallel with the 

 trabecular plate, is the " sphenoidal sinus ;" and if any osseous centres were to form in 

 the wall of this narrow region, they would be, as in Man, the " bones of Bertin," the 

 hindermost of the ossifications of the olfactory sacs. Bound strongly beneath the basi- 

 facial wall is the granular nidus of the vomer (v.), kidney-shaped in section ; and beneath 

 it the posterior nares are imperfectly floored in this the region of the palatal bone {p((.), 

 which is a centre just commencing in granular indifferent tissue less solid and clear 

 than that of the vomer. Below the mouth this section differs from the last in that the 

 dentary [d.) is thicker and lies closer to the mandibular rod [ml\). 



The fourteenth section (figs. 14 & 14") is through the middle of the eyeball, and 



MDCCCLXXIV. 2 s 



