320 



MR. W. K. PAEKER ON THE STRUCTURE AND 



In the Pig the bullar ossifications are found in a very soft stroma of connective tissue, 

 and not in thin cartilage ; yet that stroma is connected with the outer and lower edge of 

 the opisthotic and prootic regions ; it is the membranous floor of this huge air-cell. 



The " OS bullae" already developed is seen in section, in its fore part (fig. 11, o.h.), a 

 little in front of the auditory capsule, at the edge of the lower limb of the tympanic 

 {ty.). The parts of the facial system of cartilages entering into the structure of the 

 middle ear are shown in figs. 1 & 12 ; the "manubrium mallei" (fig. 1, mh.) is now 

 ossified, and so also is the incus (figs. 12, ?'.). The lingual part of the hyoid arch is con- 

 tinued upwards to the epiotic region (figs. 1 & 5, st.h.), and behind this flattened rod 

 the portio dura nerve is seen escaping. 



The little ceratohyal {cJty.) turns backward to articulate with the basal piece, to 

 which also is attached the thyrohyals (fig. 1, b.h., t.hy.); the latter three parts belong 

 to the " third postoral arch." 



The ossification of the lower jaw (fig. 1, d.) is almost complete, the unossified cartilage 

 being principally condylar. 



A series of sections selected from a large number now remain to be described ; they 

 will more fully illustrate this stage. 



The first of these (Plate XXXV. fig. 6) is through the anterior third of the " inferior 

 turbinal the pedate lower edge of the " aliseptal " cartilage here is seen to be coiled 

 inwards above and below, the common back of the two coils lying towards the septum 

 {i.th., s.n.). The sudden inbend of the aliseptal lamina higher up is the rudimentary 

 " nasal turbinal " [n.th.) ; below the septum is the vomer [v.), and below this the palatine 

 processes of the premaxillaries are seen ( j^.p.f.). The nasals [n.), the side of the pre- 

 maxillaries, and maxillaries {j)X., mx.) show very thick in the section. On each side of 

 the vomer the "recurrent apices of the trabecular horns" are still present [rcc). 



The second section (fig. 7) is through the complex upper and middle turbinal regions 

 (u.tb., m.th.) and the high part of the perpendicular ethmoid []).e.). The olfactory 

 crura (1) are also cut through as they lie on the cribriform plate (cr.j).). This widest 

 part of the true olfactory region is roofed in by very massive frontals (/'•); the thin 

 lower edge of these bones is the orbital plate. The vomer (v.) is here very deep ; on 

 each side of it the posterior nares arc cut through, and these are protected by the 

 long scoop-shaped processes of the palatines (jia.). A part of the maxillary is seen 

 on each side of a large molar tooth with its pulp ; and above, the outer piece of bone is 

 the jugal (j.). 



The third section (fig. 8) is through the low part of the perpendicular ethmoid and 

 the end of tlie cribriform plate, where it overlies the middle turbinal (m.tb.) only. The 

 palatines (j^a.) are here at their fullest development, their scooped portion underlying 

 the end of the nasal wall {n.w.), and their subvertical plate sending inwards the palatal 

 part of the hard palate. 



with the head of n ncw-borii Ilynix ; in (liis I found a largo bulla, ossified separately from the true tym- 

 panic " anuuluH," and cvidenlly formed in a slicll of true eartilage. 



