45 



PLATE XXII. 



THE F-RiOGr continued. 



SENSE ORGANS 



FIG. 1. EYE OF Ox divided (a) Into a right and left half left half shown. 



(b, c) Along equator into an anterior and posterior half. 

 Sclerotic or outer coat passing into transparent cornea in front. 



Ghoroid coat pigmented, anterior end raised into longitudinal plaits the ciliary processes. 

 Iris (L. a rainbow), anterior to ciliary processes, and connected to sclerotic where it passes into 



cornea by the ciliary muscle. 

 Lens enclosed in capsule, which is attached to the inner side of the choroid by suspensory 



ligament. 



Ciliary muscle dips into folds ol ciliary processes above, just as suspensory ligament dips into them below (b). 

 Aqueous humour anterior to lens. 

 Vitreous humour posterior to lens. 

 Eetina inside clioroid. 



Optic nerve entering a little to one side of axis by the optic pore. 

 Fio. 1 c. Blood-vessels are seen to enter retina from the spot where optic nerve enters. 

 Fio. 2. GENERAL VIEW OP EIGHT EAR OF FROG 



Tympanic cavity exposed by removing tympanic membrane. 

 Three semicircular canals. 

 Columella auris (L. little column of the ear). 

 FIG. 3. MEMBRANOUS LABYRINTH OP LEFT EAR 



Semicircular canals, anterior, posterior, and horizontal, each dilated at one end into ampullae 



(L. ampullor, I swell out), and two ends of vertical canals joining together. 

 v .. . ( Utriculus (L. a little bag), into which semicircular canals open. 



' ' \ Sacculus (L. a small bag). 

 Cochlea (L. a snail's shell), rudimentary. 

 FIG. 4. ESSENTIAL PARTS OP HUMAN EAR, natural size 



External ear Pinna or concha (L. a shell), not shown. 

 , Auditory meatus (L. a canal). 

 Tympanic membrane. 

 Tympanic cavity or tympanum opening by Eustachian tube into pharynx. 



f Malleus (L. a hammer). 

 -| Incus (L. an anvil). 

 V. Stapes (L. a stirrup). 

 Fenes'tra ovalis (L. oval window), an oval membrane, to which foot-plate of 



stapes is attached. 

 Fenestra rotunda (L. round window), at the base of cochlea. 



( Semicircular canals, horizontal not shown. 

 Internal ear or 1 T , ... , . . ... 



labyrinth ) Vestibule into which canals open. 



(. Cochlea, also communicating with vestibule. 

 FIG. 5. AUDITORY OSSICLES OF HUMAN EAR, magnified. 

 FIG. 6. COLUMELLA AURIS detached (see also fig. 2) 

 Stapes or inner end fits into fenestra ovalis. 

 Extra-stapedial or onter end attached to tympanic membrane. 



Middle ear 



Auditory ossicles or ear-bones bridging over cavity -| Incus (L. an anvil). 



