94 LABORATORY OUTLINE OF NEUROLOGY 



junctivum; at the upper border of the pons they turn inward 

 and can be followed downward dorsally of the deep fibers of the 

 pons to the superior olive. This small nucleus is difficult 

 to identify, since its cell bodies are scattered among the fibers, 

 but its position is indicated at the place where the lemniscus 

 fibers turn abruptly medialward. (Compare the next paragraph 

 for the relations of the spinal lemniscus to the lateral lemniscus 

 and Section 82 for the microscopic appearance of this region.) 



107. Having traced the fibers of the lateral lemniscus back- 

 ward to the superior olive, the ventral spino-cerebellar tract 

 (of Gowers) and the spinal lemniscus (see Section 105) may now 

 be traced from the lower border of the pons to the upper border 

 of the superior olive, where they will be seen to accompany the 

 lateral lemniscus from this level forward. The ventral spino- 

 cerebellar tract accompanies the lateral lemniscus complex 

 into the midbrain, where its fibers may be seen to sepa- 

 rate from the others and to enter the cerebellum by the way 

 of the brachium conjunctivum, lying more superficially than 

 the tract from the dentate nucleus to the red nucleus. 



108. The medial lemniscus. — Identify again the nucleus 

 of the fasciculus gracilis and the nucleus of the fasciculus 

 cuneatus. These receive proprioceptive fibers from the spinal 

 cord by way of the fasciculus gracilis and fasciculus cuneatus. 

 The cell bodies of these nuclei send their axones to the thalamus 

 by way of the medial lemniscus. In the pons region this 

 lemniscus lies ventrally and medially of the superior olive and 

 medially of the lateral lemniscus, whose fibers it adjoins during 

 their course through the upper pons and midbrain regions. 



Identify the medial lemniscus in the region of the superior 

 olive. It will be found as a broad band of longitudinally directed 

 fibers near the midplane immediately dorsally of the deepest 

 fibers of the pons. Tracing them downward they become 

 crowded into the space between the two inferior olives. Under 

 the nuclei of the fasciculus gracilis and fasciculus cuneatus these 

 fibers cross the midplane and then turn abruptly dorsalward in 

 numerous strands to connect with these nuclei of the opposite 

 side. 



In the dissection of the medial lemniscus in the medulla ob- 

 longata care must be taken not to destroy the pyramidal tract 



