41 



PLATE XXI. 

 iTITTTn i|i [_&amp;gt; f~\(~V . 7 



\ t~\ Pi J? JTuV-lvT continued. 



NERVOUS SYSTEM 



FIGS. 1, 2. THE BRAIN or ENCEPH ALON (Gr. en, in ; kepha.lt&amp;gt;, the head) 



Olfactory lobes or Khinenceph alon (Gr. rhis, rhinot, the nose) giving oil 



olfactory nerves. 



, Cerebral hemispheres or Prosenceph alon (Gr. pros, before) completely 

 OHE-BIIAIN ^ separated by the great fissure (fig. 3). 



I Optic thalami ((!r. thalamns, a bed), one on each side bounding the third 



ventricle with pineal gland on roof.=Thalaiiionceph alon. 



Mii&amp;gt;BuAiN f Optic lobes above and crura cercbri (L. legs of the cerebrum) below. = 

 (Yellow) ( Mesenceph alon (Gr. meson, middle). 



/Cerebellum (L. the little brain), very small = Metenceph alon (Gr. ultta, 

 3 behind). 



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

 V Myelonceph alon ((Jr. muelos, marrow). 



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

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

 FIG. 3. THE CAVITIES OF THE BRAIN, so-called Ventricles 



1. Olfactory. 



2. Lateral . ) 



o n ,i j , Aperture of communication, foramen of Munro. 



3. llurd ventricle j 



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

 ventricles of optic lobes entering it. 



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



Fio. 4. GENERAL VIEW OP THE BRAIN AND SPINAL CORD, 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. Teu pair of CRANIAL NERVES, ten pair of SPINAL NERVES, and ten pair of SYMPATHETIC 



GANGLIA 

 CRANIAL NERVES, 1 to 10 (yellow). 



Spinal 1, hypoglossal (Gr. Jmpo, under ; ;/lvssa, a tongue), distributed to 



tongue. 



,, 2 and 3, forming a brachial plexus (L. brachium, an arm ; plexus, 

 a junction), and distributed to fore-limbs. 



SPINAL NERVES 

 (Blue) 



/ ,, 4, 6, and G, distributed to the body-walls. 



7, 8, and 9, forming a lumbo-sacral plexus (L. lumlns, the loin). 



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

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

 to back of it. 



10, distributed to parts about coccyx. 

 SYMPATHETIC GANGLIA (S. 1 to S. 10), with connecting commissures (red). 

 DIAG. 2. CONTENTS OF NEURAL CANAL, as seen in a transverse section 



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



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

 SPINAL COUD -\ Central canal lined with epithelium. 



,., ., .., ( Posterior fissure (dorsal). 



\\ hite matter outside grey matter J 

 L. ( Anterior fissure (ventral). 



f 



