54 



Anatomy of the Rabbit. 



closing the aperture for transmission of the spinal cord from the 

 cranial cavity. The basisphenoid and presphenoid bear lateral 

 expansions, respectively the greater and lesser wings, or ali- 

 sphenoids and orbitosphenoids, which assist in the formation 

 of the side walls of the brain case. The bone capsule (periotic) 

 lodging the internal ear on either side is solidly built into the 

 lateral cranial wall between the exoccipital and alisphenoid, while 

 further forward the light scroll-like surfaces of the ethmoid bone, 

 or ethmoturbinal, representing the chief portions of the nasal 



Fig. 28. 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 (I); e, mesethmoid; et, ethmoturbinal; ex, exoccipital; 

 f, frontal; hy, hyoid 1 1 1 1 ; i. incisors; 1, lacrimal; m, molar teeth; mn, mandible; 

 mx, maxilla; mt, maxilloturbinal; n, nasal; nt, nasoturbinal; os, orbitosphenoid; 

 p, premaxilla; pa, parietal; pi, palatine; pm, premolar teeth; pt, pterygoid; 

 sq, squamosal; so, supraoccipital; th, thyreohyal (III) ; v. vomer; z, zygomatic. 



capsule is attached on each side of the base of the mesethmoid. 

 The original proportions of the nasal capsule are however more 

 nearly commensurate with the general cavity of the nose; and 

 additional turbinal surfaces, comprising the nasoturbinals and 

 maxilloturbinals are attached secondarily to the nasal and 

 maxillary bones. 



To this foundation there is added a series of enclosing 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 the interparietal (absent in the hare and many mam- 



