114 LABORATORY OUTLINE OF NEUROLOGY 



They run just in front of the optic radiations and end in the 

 temporal lobe of the cortex. 



149. Somesthetic radiations. — Carefully tease the lateral and 

 medial lemniscus fibers from the midbrain region, into which 

 they have been traced (Sections 106 and 108), upward into 

 the thalamus. Their terminal nuclei comprise the lateral and 

 ventral nuclei of the thalamus, lying internally of the pulvinar. 

 From these nuclei strands of fibers can be torn upward toward 

 the cortex into the internal capsule. These are the somatic 

 sensory radiations destined for the gyrus centralis posterior. 



150. Pyramidal tract. — Next tear the pyramidal tract upward 

 from the midbrain floor along the cerebral peduncle into the 

 internal capsule. These are descending fibers from the gyrus 

 centralis anterior. 



151. Brachium conjunctivum. — Finally, tear the fibers of the 

 brachium conjunctivum downward to their decussation under 

 the aqueduct of Sylvius. The red nucleus or nucleus ruber 

 (where these fibers end after decussating) will be seen imme- 

 diately in front (cephalad) of this decussation, as a round gray 

 mass about the size of a pea, not far from the median plane. 

 Its rubro-thalamic tracts can readily be seen by teasing for- 

 ward from the nucleus. 



152. Thalamic nuclei. — Now make a list of the nuclei of the 

 diencephalon which you have seen and tabulate their fiber 

 connections. 



12. Recapitulation of Conduction Paths 



153. Finally, having completed the Table of Conduction 

 Pathways (Section 101) and a table or diagram of the olfactory 

 tracts (Section 130), make a systematic review of each functional 

 system of tracts. For each system get a clear picture of the 

 course of the nervous impulses involved in both the reflex and 

 the cortical functioning of that system. With the intact 

 human brain before you, try to visualize the courses of the 

 fiber tracts in question with reference to the external landmarks. 



