DEVELOPMENT OF THE NERVOUS SYSTEM. 



41 



Fig. 20. — Reconstruction of the brain and cerebral nerves in a 12 mm. pig 

 embryo. (From Minot's " Laboratory Text-Book of Embryology." Drawn and 

 revised by F. T. Lewis.) 



Nerves. 3, oculomotor. 4, trochlear. 5, trigeminal, with its semilunar ganglion, 

 s-l, and three branches, — oph., ophthalmic; tnx., maxillary; md., mandibular. The 

 motor portion, which goes with the mandibular branch, is concealed in this view 

 by the sensory portion. 6, abducens. 7, geniculate ganglion of the intcrmedius. 

 Fibers from this ganglion mix with the motor fibers of the facial nerve, so that both 

 sensory and motor fibers are found in the three branches, — /. s. p., large superficial 

 petrosal; ch. /y., chorda tympani; /a., facial. 8, acoustic, showing an upper vestib- 



