534 THE RABBIT 



CHAP. 



called taste-buds, are present on the papillae of the tongue 

 (p. 509) and on the soft palate (compare pp. 179 and 180). 

 The organs of smell are situated in the olfactory cap- 

 sules, the form of which has already been described 

 (p. 493). They open externally by the external nostrils, 

 and are produced backwards above the palate into the 

 passage of the internal nostrils, which communicate with 

 the naso-pharynx (Fig. 135, i. n, n. ph, and see p. 512). 

 The olfactory epithelium, supplied by the olfactory 

 nerves, is situated on the ethmo-turbinal (e. tb) : the 

 mucous membrane of the maxillo-turbinal (m. tb} 

 probably serves merely to warm the inspired air. 



On the ventral side of the nasal septum is a pair of small, 

 tubular structures known as the vomcro-nasal or Jacobson's 

 organs (Fig. 135, j), lined by epithelium and enclosed in 

 cartilages situated just to the inner side of the palatine pro- 

 cesses of the premaxillye (p. 494). Each of them opens 

 anteriorly into the corresponding naso-palatine canal (p. 507), 

 and receives a special branch of the olfactory nerve. The 

 function of these organs is not understood. 



The structure of the eye is similar to that already 

 described in other Vertebrates (pp. 181 and 465), except 

 that the sclerotic is not cartilaginous, but is composed of 

 dense fibrous tissue, and the lens is relatively smaller 

 than in the dogfish and frog and is markedly biconvex 

 in form, the outer surface being rather flatter than the 

 inner : it is capable of adjustment by means of the ciliary 

 muscles contained in the radiating ciliary processes into 

 which the choroid is thrown just externally to the iris 

 (compare p. 184). 



The eyelids have already been described (p. 486). The 

 four recti muscles ensheath the optic nerve, as in the frog 

 (p. 1 86, compare Fig. 126), but the superior oblique, instead 

 of arising like the inferior oblique in the anterior part of 

 the orbit, takes its origin further back, near the recti, passes 

 forwards through a fibro-cartilaginous pulley at the anterior 

 angle of the orbit, and then backwards and outwards to its 

 insertion on the eyeball. 



