164 ELEMENTABT BIOLOGY. [XIII. 



and partly cartilaginous bar is given off, which is perforated 

 at its origin by the canal for the orbito-nasal nerve. It then 

 narrows, but becoming flattened from above downwards, 

 rapidly widens again, and its axe-head-like extremity abuts 

 against the inner face of the maxilla. The anterior angle of 

 the axe-head is free ; the posterior angle is continued back 

 into a slender cartilaginous pterygoid rod which bifurcates 

 posteriorly. The outer division passes into the ventral crus of 

 the suspensorium. The inner division is the pedicle of the sus- 

 pensoriuTii; it articulates by a joint with the anterior face of 

 the broad lateral process of the. hinder part of the chondro- 

 cranium, which contains the auditory labyrinth and is termed 

 the periotic capside. The Suspensorium is a rod of cartilage, 

 which lies between the squamosal and the pterygoid bones 

 and, at its distal end, articulates with Meckel's cartilage which 

 forms the core of the ramus of the mandible. At its dorsal 

 end it divides into two divergent processes or crura, of which 

 the ventral crus has already been said to be continuous Avith 

 the pterygoid. The dorsal crus, on the other hand, passes up- 

 wards and, curving backwards, becomes attached to the dorsal 

 part of the outer face of the periotic capsule. 



Meckel's cartilage, articulated to the free end of the sus- 

 pensorium, is tmossified throughout the greater part of its 

 extent, no osseous articulare being developed; but, at its 

 symphysial end, each cartilage becomes ossified, and forms 

 the mento-Meckelian element of the mandible. 



The slender, cartilaginous band {cornu of the hyoid) by 

 which the body of the hyoid is attached to the skull, is con- 

 nected with the periotic cartilage immediately in front of 

 and below the fenestra ovalis. 



The pectoral and pelvic arches (see Laboratory work D.e.g.) 

 are, in the young state, undivided cartilages on each side, and 

 the development of bone in and upon them does not really 

 destroy this continuity, the cartilage persisting at the ends of 



