IO2 NERVOUS SYSTEM OF VERTEBRATES. 



forming the tractus spino- and bulbo-tectalis (lemniscus), tec- 

 turn mesencephali, and other nuclei, 

 tertiary tracts to motor nuclei and coordinating centers. 



2. Special cutaneous subdivision. Consists of: 



neuromasts (acustico-lateral sense organs), 

 neuromast components, 



spinal VIII tract and nucleus, nucleus funiculi, acusticum, cere- 

 bellum, secondary tracts and centers and tertiary tracts as in i, 

 the cochlea, its nerve and centers in higher vertebrates. 



3. Special sense organs belonging to the somatic sensory division. 



Lateral eyes. Consist of: 



retina, which includes the equivalent of sensory ganglion, nerve 



component, and primary brain center, 

 optic tract and tectum opticum corresponding to the secondary 



tracts and centers of the cutaneous subdivision. 

 Pineal eyes. (Compare Chap. VIII below.) 



B. Visceral sensory division. 



1. General visceral subdivision. Consists of: 



free nerve endings in the mucosae, 



fasciculus communis system of components, 



CLARKE'S column or its equivalent, nucleus commissuralis CAJAL, 



lobus vagi, and lobus facialis, 

 secondary visceral tract and its continuation in the cord,=the 



direct cerebellar tract in higher forms, 

 secondary visceral nucleus,=end nucleus of direct cerebellar tract 



in the vermis of higher forms, 

 tertiary tracts to the hypothalamus in lower vertebrates. 



2. Special visceral subdivision. Consists of: 



end buds (taste buds) : 



components and central nuclei and tracts not yet distinguished 

 from those of the general visceral subdivision. 



3. Special sense organ belonging to the visceral sensory division. 



Consists of: olfactory epithelium and nerve, bulbus olfactorius, 

 tractus olfactorius, area olfactoria, and tertiary tracts to coord- 

 inating centers in the diencephalon. 



4. Sympathetic system, afferent portion. An outgrowth or offshoot 



from visceral sensory ganglia which reaches a high specializa- 

 tion in the vertebrate series. Consists of simple visceral 

 sensory component fibers and of ganglion cells which together 

 with the efferent portion control contraction of smooth muscles 

 and glandular secretion. 



C. Somatic motor division. Consists of: 



ventral horn of the cord, nuclei of origion of Nn. XII, VI, IV, III, 

 and nucleus of somatic motor fasciculus, 



