166 Anatomy op the; Rabbit. 



body, the whole structure, together with the hyoid, larynx, and a por- 

 tion of the trachea back to about the end of the thyreoid gland may be 

 removed. This affords a good opportunity of re-dissecting on the oppo- 

 site side from the medial surface of the mandible outward, also of clearing 

 and examining the hyoid apparatus, which is not usually available with 

 the prepared skeleton (p. 97). The laryngeal cartilages should be 

 cleared externally and the parts made out as follows: 



(a) The thyreoid cartilage (cartilago thyreoidea) (Fig. 36) forms 

 the largest portion of the structure. It is a unpaired saddle- 

 shaped cartilage, described as consisting of right and left 

 laminae. Its anterodorsal angle projects forward as the 

 cornu superior; connected by ligament with the greater 

 cornu of the hyoid. The corresponding posterodorsal angle, 

 the cornu inferior, overlies the dorsolateral portion of the 

 cricoid cartilage. The anterior dorsal portion of each plate 

 bears a small thyreoid foramen (foramen thyreoideum) for 

 the entrance of the superior laryngeal nerve. 



(b) The cricoid cartilage (cartilago cricoidea) is an annular carti- 

 lage, partly enclosed by the posterior portions of the thyreoid 

 laminae and surrounding the first tracheal ring. Its ventral 

 portion, the arch of the cricoid cartilage, falls some distance 

 behind the thyreoid cartilage, the intervening space being 

 largely occupied by the cricothyreoidei muscles. Its dorsal 

 portion, the lamina of the cricoid, forms a greatlv expanded 

 plate serving for the support of the arytenoid cartilages. 



(c) The paired arytenoid cartilages (cartilagines arytenoideae) lie 

 one on either side of the anterior tip of the cricoid plate. 



(d) The corniculate cartilages (cartilagines corniculatae) are 

 slender curved terminal cartilages supported by the ary- 

 tenoids. 



(e) The epiglottic cartilage (cartilago epiglottica) is a triangular 

 plate supporting the epiglottis. 



(f) The rudimentary vocal folds (plicae vocales) may be seen as 

 vertical folds of the internal surface of the larynx, especiallv 

 prominent when the thyreoid cartilage is bent downward on 

 the cricoid. Each fold forms the posterior boundary of a 

 shallow pouch, the laryngeal ventricle (ventriculus laryngis). 



In addition to the criothryreoidei the laryngeal cartilages are 

 connected by several small muscles, including the cricoarytenoidei 

 posterior 'and lateralis, the thryreoarytenoideus and the arytenoideus 

 transversus, the last named being an unpaired muscle connecting the 

 arytenoid cartilages. 



11. The eye and related structures of the orbital cavity. 



The eyeball should be carefully separated from the bony orbital rim- 

 The first portion of the nasolacrimal duct (d. nasolacrimalis), passing 

 from its aperture on the medial surface of the lower eyelid to the lacrimal 

 bone, will be divided. The muscles and glands of the orbit may be 

 made out as follows: 



