258 



THE CAT. 



[chap, IX. 



dorsally, of which the first or " aiiicrior* median fi>imre" is the 

 more distinct, aud a process of the pia mater is prolonged into it, 

 which is not the case as regards the jJOHtcvior jiiedicni fiHanrc. 



Each Lateral half of the spinal cord is also marked by two longi- 



Fig. 124. — Different views of a portion of tub Spinas Cokd from the Cervical 

 Region, with the Roots op the Nerves, eni.aroed (Allen Thomson). 



Ill .1 lliu ventral nr anturinr snrfare is shown, 

 tli<'. anterior ncrvc-ruDt of the vi;,'lit siile 

 lieiii;; divideil ; in II, a. view of tlie. i i;,'lit siile 

 is given ; in (', tlie aiiterinr or njijier surface 

 is sliown ; in I), tlie nerve-roots ami ganglion 

 ale sluiwn from beldw. 



1. Tlie anterior meilian fissure. 



•J. I'dstcrior meilian fissure. 



3. Anterior lateral (le|iressi(in, over wliieli the 

 anterior nerve-ruuts are seen td s])i-eail. 



Posterior lateral groove, into whieli the \hu- 



terior roots are seen to sink. 

 Anterinr routs passing the ganglion. 

 , III A the anterior root divided. 

 The iMisterior roots, the fibres of which l>a.s.'> 



into the ganglidii, (>'. 

 The united cir eomiiound nciTc. 

 , The ])osterior primary branch, seen in A and 



1) td be derived in jiart from the aiiteridr 



and in part from tlie iidsterior I'dnt. 



tudinal furrows, of which the posterior, ov posfrrior lateral Jissurc, is 

 far the more distinct. These furrows serve to define what are called 

 the "columns" which make up the cord— each lateral half of it 

 being divided into an anterior, a lateral, and a posterior column. 

 Nervous fibres (the roots of the spinal nerves) pass out at the anterior 

 and posterior lateral furrows. 



As the nerves which so pass out traverse the intervertebral 

 foramina of the spinal column, and as the spinal cord stops (as has 

 been said) much short of the hinder termination of the vertebral 

 neural canal, it comes to pass that the nerves which pass out at the 

 sacral foramina have run back for a longer or shorter distance within 



* The torin.s "aiilcrior " ainl " po.s- 

 tcrior " refer to huiiuiii mialonij', which 

 originated tlieso names — iTpplicable to 



man with liis n]iri;,'lit attitude, hut 

 unrurtunate as aii[ilied to a (juadruiicd 

 like the cat. 



