68 LABORATORY OUTLINE OF NEUROLOGY 



somatic cochlear (Herrick ('18), Chap. XIII) and vestibular 

 (Herrick ('18), Chap. XII) are represented in the VIII nerve* 

 The connections of these systems will next be taken up, to- 

 gether with the cerebral portions of the spino-cerebral tracts 

 whose spinal parts have already been mentioned. The cere- 

 bellum, which is a derivative of the somatic sensory column, 

 will be examined later, and the composition of its peduncles 

 summarized. 



71. The general cutaneous system. The cutaneous fibers 

 from the face enter the brain by the V nerve ; a smaller number 

 by the IX and X nerves. The cell bodies of these fibers are 

 located respectively in the semilunar (V), superior (IX) and 

 jugular (X) ganglia. The fibers of the sensory V root in part 

 end in the chief sensory V nucleus dorso-medially of the super- 

 ficial origin of the root, but most of them turn abruptly spinal- 

 ward and thus form the spinal V tract, whose fibers form an 

 eminence on the lateral surface of the oblongata the tuber- 

 culum cinereum or tubercle of Rolando. 



72. Gross preparation of the spinal V tract. On the right 

 half of the brain of the sheep locate the V, IX, and X roots 

 (Figs. 7, 8, 12) and the tuberculum cinereum. Now with a 

 wooden dissector begin at the lower border of the V root and 

 carefully scrape away the transverse fibers of the pons and the 

 trapezoid body until the longitudinal fibers of the spinal V 

 tract lying immediately internal to them are exposed. Con- 

 tinue the dissection spinalward by gently teasing off the super- 

 ficial external arcuate fibers (see Section 90). Careful scraping 

 in the longitudinal direction with an orange-wood stick sharp- 

 ened to a slightly rounded chisel edge will readily expose the 

 whole length of the spinal V tract to its terminus in the cer- 

 vical cord. In its spinal course its fibers become superficial. 



A similar dissection can readily be made on the human 

 brain also, though the larger size of the pons makes it necessary 

 to cut through the large mass of the transverse pons fibers 

 below the V root with a sharp knife in order to expose the spinal 

 V fibers. This dissection, however, should not be made on the 

 same specimen which is to be used for the optional dissections 

 of the oblongata (Sections 102-111). 



73. Microscopic study of the V roots. In the microscopic 



