ZOOLOGY. 



bellum, of a medullary and cineri- 

 tious portion; but here the grey 

 c matter is central and the medul- 

 lary external. A fluid, clear and 

 limpid, discovered by Cotunni, a 

 distinguished Neapolitan physician, 

 {ills up the space intervening be- 

 '' t\vccn the arachnoid membrane and 

 I* the pia mater, by means of which, 

 10 no doubt, this extremely delicate 

 ' organ is protected from shocks and 

 other injuries. 



190. Structure of the Ence- 

 phalon. The organ is composed 

 23 of two distinct substances, the 

 cineritious and medullary ; this lat- 

 ter is fibrous, and to the tracing 



* The cerebro-spinal axis seen anteriorly : 

 the nerves have been cut through at a short 

 distance from their origin or central t> 

 tion -. a, the cerebrum ; b, anterior lobe of the 

 left hemisphere of the brain ; c, middle lobe ; 

 d, posterior lobe, almost concealed by the 

 cerebellum ; e, the cerebellum ; f t the me- 

 dulla oblongata or bulb; 1, first, or olfac- 

 tory pair of nerves; 2, second pair, or 

 optic ; 3, third pair, or motpres ocu- 

 lorum; 4, fourth pair, or pathetic; 5, the 

 fiu'iiil, or fifth pair; 6, sixth pair, or 

 abducentes ; 7, nerves of the seventh pair, 

 or facial; also the acoustic, or portio 

 mollis, by some called the auditory, and 

 viewed as a division of the seventh; others 

 call them the eighth pair; 9, the glosso- 

 nerves, called the ninth pair 



by some, by others the anterior division 

 of the eighth pair ; 10, the pneumogaatric, 

 by some included in the eighth pair, by 

 others called the tenth pair; 11, nerves o'f 

 the eleventh and twelfth pairs, the first 

 j being viewed by some as a division of the 



IT- K- n ^, i A e ig ntl > l )air > "d failed spinal accessory; 

 ric. o/.Cerebro-spmalAxis/ ( , )( , 1:lttt . r ,.,.,, ,, v gome the nillt})) } ^ 



others the twelfth, is the motor nerve of 



the tongue; 13, nerves of the thirteenth pair, or sub-o< Tij.ital : It, 15, 16, 

 tin- firM, second, and third pairs of cei \ical iu-r\.-> . _,/. cer\ic-al nerves 

 t'oniiiiii; the 1>ra<-hial jilexus ; 2">. one of the pairs of nerves of the dorsal 



rrtion of tli. spin al marrow; :n, one of the pairs of lumbar nerves ; 

 lumbar and sacral ncr\ cs forming the plexus whence come the nerves 

 of the lower extremities ; i and /', termination of the spinal niarrow, called 

 cauda eqtiina ; k, great sciatic nerve proceeding to the lower extremities. 



