446 



ZOOLOGY 



SECT. XIII 



and of simple shape, the rest have each a longitudinal groove on 

 the outer side and a transverse ridge on the crown. The first 

 pre-molar of the lower jaw has two grooves ; the second is similar 

 to those of the upper jaw. Behind the pre-molars are the molars, 

 three on each side both in the upper and lower jaws. These are 

 similar to the upper pre-molars, except the last, which is small and 

 of simple shape. 



Opening into the cavity of the mouth, or buccal cavity, are the 

 ducts of four pairs of salivary glands the parotid, the infraorbital, 

 the sub-maxillary (Fig. 1099, s. mx. gl.), and the sub-lingual (s. gl.). 

 On the floor of the mouth is the muscular tongue, covered with 

 a mucous membrane which is beset with many papillse, on certain 

 of which the taste-buds (p. 105) are situated. The roof of the 

 mouth is formed by the hard palate, which is crossed by a series 

 of tranverse ridges of its mucous membrane. Posteriorly the hard 

 palate passes into the soft palate, which ends behind in a free pendu- 

 lous flap in front of the opening of the posterior nares. At the 

 anterior end of the palate is a pair of openings the naso-palatine 

 or anterior palatine canals, leading into the nasal chambers, and into 

 them open a pair of tubular structures the organs of Jacobson (Fig. 

 1098, jcb.) enclosed in cartilage and situated on the floor of the 

 nasal cavities. Behind the mouth or buccal cavity proper is the 



cbl 



p.niaaz 



FIG. 1099. Lepus cuniculus. Lateral dissection of the head, neck, and thorax. The 

 head and spinal column are represented in mesial vertical section ; the left lung is removed ; 

 the greater part of the nasal septum is removed so as to show the right nasal cavity with its 

 turbiuals. aort. dorsal aorta ; b. hy. basi-hyal ; cbl. cerebellum ; cer. cerebral hemispheres ; 

 cor. v. coronary vein ; dia. diaphragm ; ep. epiglottis ; eu. opening of Eustachian tube into 

 pharynx ; lar. larynx ; l.j.v. left jugular vein ; l.sb.a. left subclavian artery ; l.sb.v. left 

 subclavian vein; max. maxilla; med. medulla oblongata; mes.eth. mesethmoid ; mx.trb. 

 maxillo-turbinal ; ces. oesophagus ; olf. olfactory bulb ; pi. art. pulmonary artery ; p.max. 

 pre-maxilla ; pr.st. presternum ; pt.c. post-caval vein ; rt.l.lng. root of left lung with 

 bronchus and pulmonary veins and artery cut across ; s.gl. sub-lingual salivary glands : 

 s.mx.gld. sub-maxillary salivary gland ; st. sternebrse ; tng. tongue ; tr. trachea ; trb. ethmo- 

 turbinals ; vel. pi. soft palate. 



pharynx, which in the Eabbit is not sharply marked off from the 

 buccal cavity, but begins where the hard palate ends. The pharynx 



