54 



ANATOMY OF THE RABBIT 



cavity of the nose; and additional turbinal surfaces, comprising 

 the nasoturbinals and maxilloturbinals, are attached secondarily 

 to the nasal and maxillary bones, the maxilloturbinals occupying 

 only the respiratory or non-olfactory portion of the cavity. 



To this foundation of cartilage bones there is added a series of 

 enclosing membrane bones, for the most part thin and superficial, 

 but nevertheless making up the greater part of the facial portion 

 of the head skeleton as opposed to the cranial or brain-containing 

 portion. The series comprises a median interparietal (absent in the 

 hare and many other mammals), paired parietal, squamosal, frontal, 



mT^' 



Fig. 30. Composition of the mammalian skull. Cartilage dotted, cartilage 

 bone shaded, derm bones plain: I-XII, cranial nerves; as, alisphenoid; bh, 

 body of hyoid; bo, basioccipital; bs, basisphenoid; c, canine teeth; cm, 

 Meckel's (mandibular) cartilage (visceral arch I): e, mesethmoid; et, ethmo- 

 turbinal; ex, exoccipital; f, frontal; hy, hyoid (visceral arch 11); i, incisors; 

 1, lacrimal; m, molar teeth; mn, mandible; mx, maxilla; mt, maxilloturbinal; 

 n, nasal; nt, nasoturbinal; os, orbitosphenoicJ; p, premaxilla; pa, parietal; pi, 

 palatine; pm, premolar teeth; pt, pterygoid; sq, squamosal; so, supraoccipital; 

 th, thyreohyal (visceral arch III); v, vomer; z, zygomatic. 



and nasal bones as roofing structures, and paired premaxillary, 

 maxillary, palatine, pterygoid, and mandibular bones forming the 

 solid supports of the mouth. Several lateral elements also take 

 part, including the lacrimal, at the anterior border of the orbit, 

 the zygomatic, forming the central portion of the corresponding arch, 

 for protection of the orbit and for muscular support, and finally 

 the bladder-like tympanic bone, which forms the enclosure of the 

 middle ear and protects the delicate bones of the auditory chain. 

 An important though inconspicuous portion of the head skeleton 

 is formed by the hyoid apparatus supporting the tongue, and 



