THE NERVOUS SYSTEM 139 



and glossopharyngeus nerves, or are connected with their ganglia, 

 may possibly be retrogressive in nature ; but we cannot enter 

 further into their study here, as to do so would lead us too far 

 into Comparative Anatomy, and be beyond the purpose of this 

 work. 



The variations which are continually taking place in the 

 brachial and lumbo-sacral nerve plexuses, in connection with the 

 shifting of the limbs and their girdles during development, have 

 been already considered in detail (ante, pp. 95 and 96). 



THE SYMPATHETIC SYSTEM 



Here also extraordinary variations are to be found in the 

 form, number, and size of the ganglia of the main trunks, in the 

 peripheral plexuses, and in the connections between the two chief 

 trunks ; but, except in the caudal portion of this system, we are 

 not justified in assuming that we have to do with retrogressive 

 phenomena. 



