96 COMPARATIVE PHYSIOLOGY OF THE BRAIN 



whole animal nervously as long as the supracesopha 

 geal ganglion is intact. If it is removed, the whole: 

 influence of this so-called sympathetic nervous system 

 ceases. It is possible that the stimuli which pass 

 from the sympathetic into the central nervous system 

 may condition the alternation of rest and activity 

 which characterises the normal animal, and that the 

 removal of this stimulation may remove the necessity 

 of resting. 



Maxwell has found that a Nereis which has lost the 

 suboesophageal ganglion becomes quiet. Such ani- 

 mals make no attempt at burrowing. The reason for 

 this is that the motor nerves of the oesophageal mus- 

 cles originate in the suboesophageal ganglion, so that 

 removal of this ganglion causes paresis or paralysis of 

 these muscles. The pharynx plays a great role in bor- 

 ing the hole. It is due to this same paralysis or paresis 

 of the cesophageal muscles that a Nereis no longer 

 eats after losing the suboesophageal ganglion (5). 



We wish to mention here, however, that removal 

 of the suboesophageal ganglion does not bring about 

 disturbances in taking up food mall Annelids. Max- 

 well found that the leech is still able to suck itself full 

 of blood after losing the ganglion. McCaskill dis- 

 covered, however, that in the leech the motor nerves 

 of the sucking apparatus originate in the supra- 

 oesophageal ganglion. The suboesophageal ganglion in 

 the leech behaves like the first link in the ganglion- 

 chain. 



As regards the restlessness of Nereis after removal 



