68 



ventral pair posterior to these, which give off the visceral 

 nerves (fig. TO, Ant. Vise. G. and Vise. G.). 



Commissures — Short stout commissures conned the 

 sub- and supra-oesophageal nerve masses. There are two 

 such pairs, the posterior being the broader: (1) the 

 anterior pair, uniting the cerebral and brachial ganglia, 

 and (2) the posterior pair, uniting the cerebral and 

 viscero-pedal masses. 



.Verves. 



From the brain are given off numerous pairs of 

 nerves, which innervate the different regions of the body. 



A. The nerves given (ill from the cerebral ganglia 

 are:— (1) Optic, (2) olfactory, (3) labial (4 pairs), ill 

 buccal, (5) anterior superior ophthalmic nerves, and the 

 motor nerves of the eyeball. 



13. The nerves given off from the sub-oesophageal 

 mass are: (1) Posterior superior ophthalmic, (2) inferior 

 ophthalmic, and the motor nerves of the eyeball, ( ; !i 

 anterior infundibular, (4) posterior infundibular, (5) 

 visceral, (0) pallia], (7) accessory pallia!, (8) anterior 

 vena cava!, (9) auditory, (10) brachial, (11) interbrachial, 

 and (12) the nerves of the head. 



A. (1) The Optic nerves are stout, rather short 

 nerves running straight out from the lateral region of the 

 cerebral ganglion at the level of the posterior groove 

 (fig. TO, Ojjt.N.). In section the optic nerve is oval. 

 and piercing the cranial cartilage it enters the orbit 

 and there expands into a large oval optic ganglion from 

 which are given off nerves to the retina (PI. IX, fig. 71, 

 T\.X.). These optic ganglia are each greater in bulk 

 than the two supra-oesophageal ganglia, and are about 

 twice as long as they are thick. Internal to the optic 

 ganglion, on the dorsal side of the optic nerve, is a much 



