384 STRUCTURE OF VERTEBRATES. 



DIAGRAM XXII. 

 Nervous System. 



The longitudinal section of the brain, Sect. Brain (after Wiedersheim 

 and Huxley), shows I. the fore-brain, with olfactory outgrowths iplf.), 

 and ganghonic corpus striatum (c. j.) on its floor; 2. the tween -brain, 

 with pineal outgrowth (p.) above, infundibulum (t. ) bearing the hypo- 

 physis (,^. ) beneath, and optic nerves ippt.) running forward; 3. the 

 optic lobes ; 4. the cerebellum ; 5. the medulla oblongata, with its thin 

 roof; the spinal cord {s. c). Beneath lies the notochord {N. ch.). 



The figure named Sf. canal shows (after Sutton) the three primary 

 vesicles [a. b. c.) of the brain, the pineal upgrowth (/.), the hypophysis 

 {BT.), the notochord {JV. c/i.), ^ihe gut (C), the neurenteric canal (N.), 

 the yolk-sac ( K. ). 



Beneath is a diagrammatic section of the spinal cord, showing the 

 dorsal furrow (d. f.), the ventral furrow {v.f.), the minute canal in the 

 centre, the external white matter {w. m.), the internal grey matter 

 {g. m.), the dorsal, anterior, or sensory roots {d. a. s.) with a ganglion, 

 the ventral, posterior, or motor roots {v. p. m.), their union in a nerve, 

 the sympathetic ganglia {s. g.) connected to the ventral roots. 



The figure Ear (after Balfour) shows the primitive auditory vesicles or 

 insinkings (au. v.), the brain (ir. ), the notochord {JV. ch.). 



The figure iVtfjs (after Balfour) shows ihe primitive nasal pits (olf.), 

 the adjacent olfactory lobes [olf. v. ) of the cerebral hemispheres (c. h. ). 



Eye I. (after Balfour) shows the origin of optic vesicles {op. v. ) from 

 the fore-brain (/ b.), and the pad of skin (/.) which will form the lens. 



Eye II. (after Balfour) shows the relation of the lens (/.) to the in- 

 dimpling optic vesicle (pp. v. ). 



Eye III. (after Balfour) shows how the lens (/.) and the retina {ret.) 

 are formed. 



Eye IV. (from Hatschek, after Arlt) shows a horizontal section of the 

 human eye. The cornea {c), aqueous humour {a. h.), iris («.), lens (/.), 

 ciliary process [c. p.), vitreous humour [v. h.), retina (n), choroid {ch.), 

 sclerotic {sc), yellow spot {y. sp.), optic nerve (?/.), and its sheath are 

 indicated. 



