H2 ZOOTOMY. 



64. The epipterygoid (e.pt.) (so-called columella), a 

 slender rod of bone, lying just in front of and external to 

 the anterior edge of the prootic : below it articulates with 

 the pterygoid, above with the prootic. 



65. The columella auris (Fig. 36), a small rod of 

 combined bone and cartilage, lying in the dorsal wall of the 

 tympanic recess : its inner end is inserted into the fenestra 

 ovalis, a small aperture between the prootic and opisthotic, 

 while its outer end is, in the entire head, fixed to the inner 

 surface of the tympanic membrane. 



i.at 



jf CM 



FIG. 36. Lacerta agilis. The columella auris (after W. K. Parke?) 

 x 14. The cartilaginous parts are dotted. 



e.st, extra- stapedial : i.st, infra-stapedial : m.st, medio-stapedial : 

 s.st, supra-stapedial : st. stapes. 



The columella auris consists of the following distinct parts which 

 are only to be made out by careful dissection of an entire head : (a) the 

 stapes, (st), a small cartilaginous nodule in the fenestra ovalis : (b) the 

 medio-stapedial (m.sf), a bony bar connected with the stapes, the 

 ossification from it extending into the latter : (c) a. cartilaginous rod 

 continuous with the distal end of the medio-stapedial, sending off a 

 downwardly directed process, the infra-stapedial (i.st), and expanding 

 at its outer or free extremity into a bar set transversely to the rest of the 

 columella like the head of a hammer : the lower somewhat pointed end 

 of this bar is the extra-stapedial (e.st) : its dorsal extremity, the supra- 

 stapedial (s.st) is blunt and rounded, and gives off a process which 

 becomes connected with the auditory capsule. 



66. The vagus foramen (Fig. 35, IX, X, XI,), a small 

 aperture in the combined exoccipital and opisthotic, behind 



