41 



PLATE XXL 



THE FROGr—contmued. 



Fore-Braix -{ 



Mid-Bi;aix 

 (Yellow) 



Hind-Bkaix 



Nervous System — 



Figs. 1, 2. The Bsain or Enceph'alon (Gr. ««, in ; hephale, the head) — 



-Olfactory lobes or Ehinenceph'alon (Gr. rhU, rhinos, the nnse) giving oil' 



olfactory nerves. 

 Cerebral liemispherea or Prosencephalon (Gr. 2»'os, before) completely 

 separated by the great fissure (fig. 3). 

 I Optic thalami (Gr. thalamos, a bed), one on each side bounding the third 

 L ventricle with pineal gland on roof.=Thalaiuenceph'alon. 

 ( Optic lobes above and crui-a cerebri (L. legs of the cerebrum) bslow.= 

 ( Mesenceph'alon (Gr. meso.% middle). 



/"Cerebellum (L. the little brain), very small =Metenceph'alou (Gr. nteta, 

 \ behind). 



) Medulla oblongata (L. elongated marrow) with the fourth ventricle. = 

 \ Myelonceph'alon (Gr. muelos, marrow). 

 Lamina terminalis (L. terminal plate), the anterior wall of the tlialamencephalon ter- 

 minating the axial portion of the brain, the hemispheres being lateral expansions. 

 Fig. 3. The Cavities or the iiuAiN, so-called Ventricles — 

 1. Olfactory. 



r mi . 1 ■ , r Aperture of communication, foramen of Munro. 



3. Third veutncle ) ^ 



Iter a tertio ad quartnm veutriculum (L. passage from third to fourth ventricle), with 

 ventricles of optic lobes entering it. 



4. Fourth ventricle, continuous with central canal of spinal cord. 

 Fig. 4. General View of the Brain and Spinal Coed, cerebro-spinal axis — 



Brain showing chiasma (Gr. a crossing) of the optic nerves, and optic tracts leading from optic 

 lobes. 

 Spinal cord or myelon, tapering away to the filum tenninale (L. terminal thread). 

 DiAG. 1. Tun pair of Cranial Nerves, ten pair of Spinal Nerves, and ten pair of Sympathetic 

 Ganglia — 

 Ceakial Nerves, 1 to 10 (yellow). 



Spinal 1, hyiioglossal (Gr. hupo, under ; ijlossa, a tongue), distributed to 

 tongue. 

 „ 2 and 3, foi-ming a brachial plexus (L. hrachium, an arm ; ;x'e.r?w, 

 a junction), and distributed to fore-limbs. 

 Spinal Nerves / „ -1, 5, and G, distributed to the body-walls. 



(Blue) \ „ 7, 8, and 9, forming a lumbo-sacral plexus (L. lumhns, the loin). 



and distributed to posterior portion of body and hiud-limbs ; 

 crural to front of limb and sciatic (contraction for ischiatic) 

 to back of it. 

 10, distributed to pai-ts about coccyx. 

 Sympathetic Ganglia (S. 1 to S. 10), with connecting commissures (red). 

 DiAG. 2. Context.s uf Neural Canal, as seen in a transverse section — 



rGrey matter, a central square with its four corners passing into the 

 I posterior (dorsal) and anterior (ventral) roots of the nerve-trunk. 



Spinal Cord -^ Central canal lined with epithelium. 



( Posterior fissure (dorsal). 



L 



White matter outside grey matter 



( Anterior fissure (ventral). 



