THE MAMMALIAN NERVOUS SYSTEM 73 



rick ('16), Fig. 72). Learn its position and enter it in the 

 sketches of the medulla oblongata and cord. 



The superior and medial nuclei send fibers into the fasciculus 

 longitudinalis medialis (posterior longitudinal bundle, see Section 

 92). Enter upon your drawings all of these vestibular tracts 

 which have been observed, including the fasciculus longitudinalis 

 medialis. See Bailey ('16), Fig. 339, p. 502; Howell ('15), Chap. 

 XXI, pp. 404-414; Piersol ('13), Fig. 1071, p. 1258; Quain ('09), 

 Fig. 158, p. 141, and Fig. 181, p\ 166; Villiger ('12), Fig. 168, 

 p. 182. 



We have now completed our first survey of the somatic sen- 

 sory systems of the spinal cord and the medulla oblongata, ex- 

 cept their connections with the cerebellum. These will be taken 

 up after the examination of the visceral sensory and the motor 

 centers of the medulla oblongata. 



84. Visceral sensory system. — In the microscopic sections 

 identify and draw the fasciculus solitarius and its nucleus. (See 

 Section 62 (4) and (5)). This fasciculus is made up chiefly of 

 root-fibers of the VII, IX, and X cranial nerves carrying both 

 general and special visceral sensory nervous impulses, the 

 special fibers being gustatory in function (Herrick '15, Fig. 114). 

 Root-fibers of some or all of these nerves may be seen in the 

 sections entering the fasciculus. Both the general and the 

 special visceral sensory fibers end in the nucleus of the fascicu- 

 lus solitarius, the gustatory fibers probably in its upper end. 

 In the region of the ala cinerea (Herrick ('15), Figs. 71 to 74) 

 the nucleus is enlarged dorsally and comes to the surface of the 

 floor of the fourth ventricle at the lateral border of the ala cinerea. 

 The fasciculus solitarius and its nucleus correspond with the 

 visceral sensory column seen in the brain of the dogfish (Section 

 23) . For the dissection of the fasciculus solitarius in the human 

 brain see Section 110. 



In connection with this section read Herrick ('15), Chap. 

 XVII, and Johnston ('06), Chap. IX. 



85. The organs of taste. — If microscopic material showing the 

 structure of the taste-buds is available it should be examined in 

 connection with the study of the visceral sensory system (see 

 Bailey ('16), pp. 229-232, 593; Cunningham ('15), pp. 854- 

 856; Sheldon ('18), Fig. 337). There has been much dispute 



