406 



;^0()LOGY 



SECT. 



its posteriur [joitiou, including the middle and posterior turbinals, 

 is invested by the one-layered epithelium ot the Schneiderian 



en ', 



B 



scLpL 



scl 



en 



pOi 



Fio. 1047. — Columba livia. The eye. A, in sagittiil section ; B, the entire organ, external 

 aspect, ca. ciirnea ; r/t. choroid ; cl. pi: ciliai-y processes; •«'/•. iris ; I. lens; opt. nr. optic 

 nerve ; 2''-"'. peeten ; rl. retina ; .s<;/. sclerotic ; sii. pi. sclerotic plates. (After Vogt and Yung.) 



membrane to which tli 

 The eye (Fig. 1047) 



-R-/-J 



V](;. 104S.— Columba livia. 



The right membranous laby- 

 rinth, outer aspect, i^.-l, am- 

 pulla of posterior canal ; FB, 

 posterior canal ; !Ll, ampulla 

 of horizontal canal ; /IB, hori- 

 zontal canal ; /a;/, cochlea or 

 lagena ; mr. membrane of 

 Kcissner ; pli, basilar part of 

 cochlea ; i'. sacculus ; SA, am- 

 pvdla of anterior canal ; SB, 

 anteriorcanal. (From Wieders- 

 heim, after Hassc.) 



e fibres of the olfactory nerve are distributed. 



is not even approximately globular, but has 

 the form of a biconvex lens. Sclerotic 

 hony plates (B., scl. pi.) are present, and there 

 is a large p)ecten (^^c^.), in the form of a 

 plaited and strongly pigmented membrane, 

 projecting into the cavity of the eye from 

 the entrance of the optic nerve. The 

 peeten is of nervous character, and is in 

 all probability a sensory organ having some 

 function connected with the process of 

 accommodation. 



The auditory organ (Fig. 1 048) is chiefly 

 distinguished from that of Reptiles by the 

 great development of the cochlea (lag). 

 The anterior canal (^S^^) is of great size, 

 and the whole membranous labyrinth is 

 closely invested by a layer of dense ivory- 

 like bone, which can be isolated by cutting 

 away the surrounding spongy bone, and is 

 then seen to form a sort of model of the 

 contained organ, to which the name long 

 lahyrinih is applied. The tympanic cavity 

 and columella have the same arrancrement 



