CHAP. IX.] AND OF BIRDS. 135 



of the general stock of afferent impressions which arouse 

 the brain activity and mental life, such as it is, of Inver- 

 tebrate animals ; and that such impressions furnish the 

 internal promptings or stimuli inciting these animals to 

 not a few of the acts and movements they are accustomed 

 to perform. 



No excuse, therefore, is needed for what might at first 

 sight seem a departure from our proper subject, in taking 

 account of this visceral portion of the Nervous System. 

 All the avenues whence impressions come to the supreme 

 centres, must, in fact, be considered by any one who 

 would properly understand the real share of the work 

 which the Brain takes as an Organ of Mind. 



The Visceral System of Nerves in Fishes, as in other 

 Vertebrates, is divisible into two main parts, which, never- 

 theless, are, to a great extent, distributed together and to 

 the same organs. There is, in the first place, a set of 

 Cerebral Systemic Nerves, represented by the Glosso- 

 pharyngeal and the Vagus or Pneumogastric and these 

 seem to be almost wholly afferent nerves conveying im- 

 pressions from the Viscera to the Medulla. Secondly, 

 there is the * Sympathetic System ' of Nerves, which, 

 though to a certain extent an independent system, is 

 also closely related to the Cerebro- Spinal Axis, by 

 means of free intercommunications passing between the 



* sympathetic ' ganglia, and the anterior spinal nerves 

 as well as most of those which are attached to the 

 medulla. 



In this latter system there are afferent and efferent 

 fibres passing between the Viscera and the several 



* sympathetic ganglia ' with which they are in relation ; 

 while these ganglia are, in their turn, connected by 

 afferent and efferent fibres with the cerebro- spinal axis, 

 in the manner above indicated. Though there may be, 



