9 6 



HISTOLOGY. 



In the diagram Fig. 113, based upon the nerves in a 12 mm. pig embryo, 

 the roots, ganglia, and fundamental branches of the cerebral nerves are 

 indicated. The ventral roots have been shaded by lines. The hypoglossal, 

 abducens, trochlear and oculomotor nerves are ventral roots only, the first 

 going to muscles of the tongue and throat, the other three supplying 

 muscles of the eye. The trochlear nerve is unique in having its neuraxons 

 pass to the upper side of the brain and cross to the opposite side before 

 emerging. Four cerebral nerves are mixed, consisting of dorsal and lateral 

 roots. Beginining posteriorly theW are the vagus (its motor part being 



FIG. 113. THE CEREBRAL NERVES OP A 12 MM. , PIG, NAMED IN THE ORDER OP THEIR OCCURRENCE 

 BEGINNING ANTERIORLY, WITH THEIR GANGLIA AND CHIEP BRANCHES. 



Olfactory (not developed). Optic (fibers in the .stalk of the eye, the lens of which is marked L). Oculo- 

 motor (Oc.). Trochlear (Tr.). Trigeminal, semilunar ganglion (s.-l.); ophthalmic (oph.), maxil- 

 lary (mx.) and mandibular (md.) branches. Abducens (Ab.). Intermedius, geniculate ganglion 

 (g.) ; large superficial petrosal (1. s. p.), chorda tympani (ch. ty.), and facial (fa.) branches. Acoustic 

 (A.), its ganglion being later divided into a vestibular ganglion, and a spiral ganglion. It supplies 

 the otocyst (Ot.). Glossopharyngeal, superior (s.) and petrosal (p.) ganglia; tympanic (t.), 

 lingual (1. r.) and pharyngeal (ph. r.) branches. Vagus, jugular (j.) and nodose (n.) ganglia; 

 auricular (au.) and laryngeal branches, rec. being the recurrent nerve; the main stem proceeds to 

 the stomach. Its accessory portion has an external ramus (ex.). Hypoglossal (Hy.). Froriep's 

 rudimentary hypoglossal ganglion (F.) sometimes sends fibers to the hypoglossal nerve, c.l, 

 C2, c.3, cervical nerves. 



called the accessory nerve), the glossopharyngeal, the intermedius (its motor 

 part and its largest branch forming the facial nerve), and the trigeminus. 

 In the diagram the lateral roots are in solid black and the dorsal roots are 

 not shaded. The accessory nerve is seen passing up the spinal cord to 

 join the vagus. A part of its fibers turn aside in the external ramus, ex, 

 to supply the trapezius and sterno-cleido-mastoid muscles; others remain 

 with the vagus to supply pharyngeal muscles, and to pass down the body 

 to the stomach. The vagus and the glossopharyngeus each have two ganglia, 



