A LABORATORY OUTLINE OF NEURO-ANATOMY 367 



olivary nuclei (Fig. 108). In the section through the middle of the pons identify the 

 lateral lemniscus. Trace this tract to the inferior colliculu,s (Fig. 114) and through the 

 inferior quadrigeminal brachium to the medial geniculate body (Figs. 114, 116). Color 

 these central connections of the cochlear nerve blue, indicating the cochlear nuclei on 

 the right side and the lateral lemniscus on the left (Fig. 134; pp. 149, 185). 



77. Dissection of the spinal tract of the fifth nerve. On the left half of the sheep's 

 brain locate the fifth nerve and tear away the transverse fibers of the pons caudal to 

 that nerve until the longitudinal fibers of its spinal tract are exposed. By carefully 

 scraping away the structures superficial to this tract follow it to the lower end of the 

 medulla. 



78. Locate the sensory nuclei of the fifth nerve in your sections and indicate them with 

 colored stipple on the right side of your drawing (pp. 154, 182; Fig. 131): the mesen- 

 cephalic nucleus, yellow (Fig. 114); the main sensory nucleus, blue (Fig. 110); the 

 nucleus of the spinal tract, blue (Figs. 98, 99, 101, 103, 107, 108). At the same time 

 color the spinal tract of the right side blue. What becomes of the fibers which arise 

 from the cells of the main sensory and the spinal nuclei of the trigeminal nerve? (See 

 pp. 183, 307; Fig. 232.) 



79. From the text ascertain the course of the spinothalamic tract and trace it up 

 through the brain stem (Figs. 105, 230, 231, 234). Where do these fibers come from, 

 and where do they end? What kind of sensations do they mediate? Enter it in blue 

 on the right side of your drawings. (See pp. 101, 102, 145, 305.) 



VISCERAL AFFERENT PATHS AND CENTERS 



80. Identify the tractus solitarius and its nucleus (Figs. 101, 103, 120). What is 

 the origin, termination, and function of the fibers constituting this tract? (See pp. 

 180, 181.) Indicate the tract with orange and the nucleus with orange stipple on the 

 right side of your drawing. 



VISCERAL MOTOR CENTERS 



81. In the sections of the brain stem identify the dorsal motor nucleus of the vagus 

 (Figs. 101, 103) and the following special visceral motor nuclei: the nucleus ambiguus 

 (Figs. 101, 103), the motor nucleus of the fifth (Fig. 110), and the motor nucleus of the 

 seventh nerve (Fig. 108). Stipple these nuclei purple on the left side. How are visceral 

 afferent and efferent elements connected to form visceral reflex arcs? (See pp. 174-178.) 



SOMATIC MOTOR TRACTS AND CENTERS 



82. The Corticospinal and Corticopontine Tracts. From the cerebral cortex the 

 fibers of the pyramidal tract run through the internal capsule and brain stem to the 

 somatic motor and special visceral motor nuclei of the cranial nerves and to the anterior 

 gray column of the spinal cord. Along with these it will be convenient to study the 

 cortico-ponto-cerebellar pathway. Take the left lateral half of the sheep's brain and, 

 being careful not to injure the optic tract and optic radiation, follow the fibers of the 

 basis pedunculi by dissection through the internal capsule to the cerebral cortex (Fig. 

 260) . Now tear away the transverse fibers of the pons a few at a time and follow them 

 by dissection into the brachium pontis. Observe that some of the fibers of the basis 

 pedunculi end in the pons (corticopontine fibers) and that others (corticospinal fibers) 



