THE NERVOUS SYSTEM 481 



horn. The axones of the terminal nucleus form a secondary tract to 

 the thalamus and thence a tertiary thalamo-cortical tract passes to 

 the central cortex cerebri. Axones of the mesencephalic nucleus of 

 nerve V innervate the muscle-tendon receptors of the jaw muscles 

 and nerves III, I\' and VI probably contain fibres to the muscle- 

 tendon receptors of the eye muscles. 



(3) V esUbulo-Semicircular Canal Group. — Ganglion of Scarpa of 

 VIII. The peripheral arms pass to vestibule and semicircular 

 canals. The central arms constitute the vestibular portion of VIII, 

 forming descending tracts in medulla and terminating in several 

 vestibular terminal nuclei (including Deiters' nucleus). 



(4) Acoustic Group. — Ganglion spirale of VIII. The peripheral 

 arms terminate in the organ of Corti of the cochlea. The central 

 arms form the cochlear part of VIII and terminate in the medulla 

 in various nuclei which originate the secondary tract (lateral fillet) 

 to the midbrain, and medial geniculate body in thalamus. A third 

 (or fourth?) system of thalamo-cortical neurones passes to the 

 temporal cortex cerebri (also p. 588). 



(5) Visual Group. — Ganghon in retina. The second neurone 

 system begins in the retina and forms the secondary tract (optic 

 "nerve") to the lateral geniculate body in thalamus. The third 

 thalamo-cortical neurone system passes to the calcarine cortex 

 cerebri (also p. 567). 



(6) Olfactory Group. — " Ganglion " cells in olfactory mucous mem- 

 brane form the olfactory nerve (lila olfactoria) which terminates 

 in the olfactory bulb. Secondary tracts from the olfactory bulb 

 (and tertiary tracts) proceed to diencephalon and hippocampus 

 (also p. 591). 



Efferent Peripheral (Segmental) Neurones.^(i) Splanch- 

 nic, (a) Lateral nuclei in the gray matter of the hindbrain. Their 

 axones pass to the striated voluntary muscles of the jaw (V), face 

 (VII), pharynx and larynx (IX and X). (b) Nuclei more deeply 

 placed in the gray of mid- and hindbrain. Their axones pass as 

 preganglionic fibres to sympathetic gangKa of head and body, 

 (c) S>Tiipathetic. Their bodies compose the sympathetic ganglia 

 of the head (ciliary, sphenopalatine, submaxillary and otic). These 

 ganglia receive the above preganglionic fibres and are thus connected 

 with cranial nerves III, V, VTI, IX, and X. 



(2) Somatic. — Medial nuclei located near the median line in the 

 gray matter of hindbrain (XII and VI), and midbrain (IV and III), to 



31 



