154 



HIGH SCHOOL ZOOLOGY. 



tube, is coiled up like the coils of a snail's shell (from wliich 

 indeed the nam© cochlea is derived), and the branch of the 

 nerve which goes to it has to occupy the axis or columella of 

 the coil, so as to reach the whole length of the tube. 



Fig. 104. — Partly diagrammatic representation of auditory ap)iaratH3 in man. 



(The external and middle ear are in their proper position, hut tlie lahyrinth is rota- 

 ted inwards flirouirh i)ii' ; hoth tympanic cavity and lahyrinth are twice the natural 

 size, the external ear is the n.atural size), sk, auditory passajfe ; tf, tympanic mem- 

 brane , ph, t.ympanic cavity; ot. Eustachian tnlie ; h, malleus; a, incus; s, stapes ; 

 vh, ve.stibule of labyrinth; bg, semiciircular canals ; vht, scala vestihuli of cochlea; 

 tht, scala tympani, leading to fenestra rotunda, rf ; sb, temporal hone ; osd, parotid 

 gland. 



11. The mammals present just as great diversity in the 

 nature of their food and in their method of securing it as do any 

 of the lower classes, Impoitant reactions on the structure of 

 the ci'eature, especially on its intestinal system, ai-e to be ex- 

 pected, and the teeth as well as other parts are tliereby aifected. 

 Much importance is attributed by systematists to these organs, 

 because they are readily accessible to inspection, are the only 

 parts of the intestinal system preserved with the skeleton in 

 fossils, and are extremely constant, not only in number but also 

 in form, for any particulffr species. Like most mammals, the cat 



