THE RABBIT. 



113 



of scent. The sensitive epithelium consists partly of 

 ordinary columnar cells, and partly of spindle-shaped cells 

 lying between and partly below them. The latter are 

 really nerve-cells ; but in the place of branching dendrons, 

 each one sends up one fine process to the surface, ending in 

 fine projections (often called cilia, but that term is mislead- 

 ing, as they are not vibratile) which are stimulated by any 

 vapours that come in contact with them. At the lower end 

 each cell sends off an axis-cylinder which becomes that of 

 one of the non-medullated fibres of the olfactory nerve. 

 These end in arborizations 

 around nerve-cells in the /f^*\ 

 olfactory lobe. // \ 



5. The Ear of the 

 rabbit (fig. 61) is an ex- 

 tremely complicated organ, 

 of which the externally 

 visible part is the least 

 important. The essential 

 part (called the internal 

 ear, or membranous laby- 

 rinth) is quite enclosed in 

 the periotic bone. The 

 internal ear consists of 

 two sacs, indirectly united 

 by a Y-shaped tube. 

 From one of these, the 

 utriculus, three curved 

 tubes, the semicircular 

 canals, spring. The planes 

 of the three canals are 

 mutually at right angles; 

 they are respectively an 

 anterior vertical, a pos- 

 terior vertical, and a horizontal canal. There is a dila- 

 tation, called an ampulla, at the posterior base of the 

 posterior, and similar ampullae at the anterior ends of the 

 anterior and horizontal canals. These ampullae are lined 

 by an epithelium containing cells with projecting processes 

 ZOOL. 8 



Fig. 61. DIAGRAM OF EAR OF RABBIT. 



and the auditory nerve are 

 shown in black. 



