NERVES OF REPTILES. 311 



shown at 3, fig. 188. The course of the ' fourth' to the upper 

 oblique muscle is shown at 4, fig. 188. This nerve does not 

 exist, separately, in the fish-like Batrachians. 



The fifth or trigeminal nerve shows its double (ganglionic and 

 non-ganglionic) origins in all Reptiles, and its threefold primary 

 division very distinctly, in all above the Perennibranchiates. In 

 the Serpent the first division is shown at 5, fig. 188, extending 

 forward beneath the 'fourth' nerve and upper oblique muscle, 

 and above the olfactory nerve and capsule. The second division, 

 fig. 188, 6, fig. 206, 4, after communicating with the sympathetic 

 nerve, divides : one branch supplies the membrane of the mouth 

 and palate ; the other passes out by canals in the upper jaw, and 

 terminates on the follicles and substance of the upper lip. The 

 third division, fig. 188, 7, fig. 206, 5, sends branches of its non- 

 ganglionic part to the muscles of the jaws ; a large branch enters 

 the dental canal of the mandible, supplies the tooth-capsules, and 

 emerges by three or more divisions : two of these, emerging at 

 the lower part of the mandible, communicate with branches of the 

 e eio'hth ' and ( ninth ' nerves, to be distributed to the muscles and 



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parts beneath the mandibular arch : another gives filaments to the 

 membrane of the mouth as far as the sheath of the tongue ; the 

 main continuation, emerging at a foramen near the symphysis, 

 supplies the lower lip. 



In the Turtle the first or ophthalmic division of the fifth 

 advances some way in the substance of the dura mater before 

 entering the orbit ; it sends a filament to combine with one of the 



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third, to supply the ciliary nerves, without forming a ganglion : it 

 supplies the lacrymal and harderian glands, and is continued to 

 the olfactory fossa. The second or maxillary division quits the 

 third on entering the floor of the orbit, along which it curves, 

 sending from its concavity filaments to the lacrymal glands, and 

 dividing into two chief branches ; the internal branch, answering 

 to the spheno-palatine and suborbital, supplies the palate and floor 

 of the nasal cavity, and emerging at the fore-part of the orbit, it 

 spreads upon the maxillary tegument : the external branch passes 

 along the floor of the orbit, and emerges upon the face. The 

 third or ( mandibular ' division descends at the back-part of the 

 orbit, in front of the tympanic bone, supplies the temporal and 

 pterygoid muscles, enters the mandibular canal, and distributes 

 branches inwardly to the tongue and floor of the mouth, outwardly 

 to the mandibular follicles and tegument. 



In the Frog the maxillary and mandibular divisions of the 

 trigeminal, arising distinctly from the ganglion, diverge to their 



