72 LABORATORY OUTLINE OF NEUROLOGY 



courses and enter them in the outline drawings of the cross- 

 sections in their appropriate places so far as these can be 

 ascertained. 



79. Summary of secondary general somatic sensory tracts. 

 The general somatic sensory centers and tracts of the brain 

 which have now been analyzed comprise the spinal V tract and 

 its nucleus, the chief sensory V nucleus, the mesencephalic V 

 tract and nucleus, the dorsal funiculi and medial lemniscus, and 

 the spinal lemniscus. The centers mentioned receive all fibers 

 of non-visceral cutaneous and deep sensibility from the head, 

 trunk, and limbs except those serving the muscle-sense from the 

 extrinsic eye-muscles. Fibers of this character are present in 

 the III, IV, and VI cranial nerves, but of their central 

 connections nothing is known. 



From these primary sensory centers connections are made 

 through the reticular formation (see Section 89) with neighbor- 

 ing motor centers for local reflexes. All ascending tracts of the 

 second order from the primary sensory centers to the thalamus 

 are termed lemnisci. The trigeminal lemniscus and the spinal 

 lemniscus carry exteroceptive nervous impulses (general so- 

 matic sensory series) . Proprioceptive reactions are served by 

 (1) the dorsal funiculi of the cord and medial lemniscus, (2) 

 vestibular system, and (3) the cerebellar connections. The 

 first of these three belongs in the general somatic sensory series, 

 the second in the special somatic sensory series, while the cere- 

 bellum is the general co-ordination center for both of these 

 series. 



The papers of Head and his associates (see Head and 

 Thompson ('06), and Head and Holmes ('11)), may profitably 

 be read at this time; also Johnston ('06), Chapter VI. 



80. Organ of hearing. If microscopic sections are available, 

 study the cochlea and spiral organ (organ of Corti) . Accounts 

 of the structure and functioning of the internal ear may be 

 found in most of the standard text-books. See Bailey ('16), 

 pp. 580-590; Cunningham ('15), pp. 843-854; Herrick ('18), 

 Chap. XIII; Howell ('18), Chap. XX; Morris ('14), pp. 

 1092-1096; Starling ('15), pp. 505-519; Stewart ('18), pp. 

 1065-1075. For special reference, the literature cited at the 

 end of Chapter XIII (Herrick, '18) is recommended, particu-- 



