322 



CLASS REPTILIA. 



The sympathetic system consists typically of a chain of 

 ganglia on each side commencing at the upper end of the neck 

 and extending the whole length of the trunk and possibly into 

 the tail (caudal canal). Its anterior end enters the skull and 

 connects with some of the cranial nerves. In crocodiles the 

 cervical sympathetic is double as in salamanders : a deep portion' 

 lies in the vertebral- arterial canal of the ribs, and a superficial 

 in the usual position ; both are connected with the spinal nerves 

 and with each other by rami communicantes. 



The eyes are always present though they vary considerably 

 in size. The sclerotic is provided with a circle of bony plates 

 in Chelonia and .Lacertilia. A vascular pigmented fold very 



Pa-' 



Bol 



a-MirVUP 



Fio. 178. Brain of Sphenodon. Side view (after Wiedersheim). Bo? swollen termination of 

 olfactory lobe ; Ch optic chiasma ; GHS pedunculi cerebri ; Op pineal body ; HII cerebellum ; 

 Hyp pituitary body ; h small prominence in front of the cerebellum ; Jni infundibulum : 

 Lp lateral projection of cerebrum ; MH optic lobes : NH medulla oblonprata ; Pa parietal 

 organ ; Tr tractus nervi optici ; VH cerebrum ; I-XII the twelve cranial nerves. 



similar to the pec ten of birds projects into the vitreous humour 

 in most Lacertilia and in Crocodilia. A retractor bulbi is present 

 except in Ophidia. There is usually an upper and lower eyelid 

 and a nictitating membrane, but in Ophidia, Amphisba enidae 

 and geckos eyelids appear to be absent (p. 317). There are two 

 lacrymal glands, the harderian (gland of the nictitating mem- 

 brane) on the inner (anterior) side of the eyeball, and the lacry- 

 mal on the outer (posterior) side. 



Auditory organ. The membranous labyrinth as in most 

 Pisces and Amphibia is divided into a" pars superior or utricle 

 with its three semicircular canals, and a pars inferior or saccule 

 which gives off posteriorly and ventrally a cochlear process 

 (sometimes called lagena). The cochlear process is tubular in 



