112 



ZOOLOGY. 



3. Taste-organs are formed by portions of the epi- 

 thelium of the tongue. Each consists of a number of cells 

 with fine projecting processes, arranged in the form of a 

 bulb (fig. 60, B). These are not found all over the surface 



of the tongue, but 

 are aggregated in 

 areas called the 

 papillce, which are 

 easily seen by the 

 naked eye (fig. 60, 

 A). Most of these 

 are little pro- 

 jections scattered 

 around the tip ; 

 but in addition 

 there are two pairs 

 of special papillae 

 in the posterior 

 region the foliate 

 papillae are oval 

 areas crossed by 

 fine parallel 



grooves, in whose 



Fig. 60. TONGUE OF RABBIT. 



A, Surface ; B, Section through a fold of the Foliate 

 Papilla, showing three taste-bulbs. (A, natural 

 size, original ; B, greatly magnified, after Klein.) 



sides the taste- 

 bulbs occur; the circumvallate papillae are rounded pro- 

 tuberances, each surrounded by a depression : the taste-bulbs 

 are found round the sides of the protuberance. 



4. The Organ of Smell is at first, in the embryo 

 rabbit, a simple pair of sacs each with an external opening. 

 Later, internal openings to the throat are formed (posterior 

 nares). The whole epithelium of the sac is sensitive to 

 odorous vapours, and, as it develops, the epithelium with the 

 connective tissue and cartilage that surround the sac forms a 

 series of projections into the cavity of the sac : these become 

 rolled up in the complicated manner that we have already 

 noted in the skull of the dog (turbinal bones). The 

 advantage of this complication is that without any enlarge- 

 ment of the olfactory sacs, an enormous increase of the 

 sensitive surface is obtained, and so an increased keenness 



