THE CRANIAL NERVES 



891 



genito-spinal centres in the lumbar cord, a cilio-spinal centre for dila- 

 tation of the pupil in the cervical cord, and in the medulla centres for 

 sneezing, for coughing, for sweating, for sucking, for masticating, for 

 swallowing, for salivating, for vomiting, for the production of general 

 convulsions, for closure of the eyes, for the secretion of tears, and even a 

 ' diabetes ' or ' sugar ' regulating centre (p. 538). 



SECTION IX. THE CRANIAL NERVES. 



Unlike the spinal nerves, which arise at not very unequal intervals 

 from the cord, the nuclei of the cranial nerves, with the exception 

 of the olfactory and optic, are crowded together in the inch or two 

 of grey matter of '.he 

 primitive neural axis in 

 the immediate neigh- 

 bourhood of the fourth 

 ventricle and the Syl- 

 vian aqueduct. Of these 

 nuclei some are the end 

 nuclei or ' nuclei of re- 

 ception ' of sensory fibres 

 that is to say, collec- 

 tions of nerve -cells 

 around which the sen- 

 sory fibres break up into 

 terminal arborizations. 

 Such are the sensory 

 nuclei of the fifth, the 

 nuclei of the eighth, and 

 the sensory nuclei of the 

 glossopharyngeal and 

 vagus nerves (Figs. 357, 

 358). The nuclei of ori- 

 gin of the motor fibres 

 lie, upon the whole, in 

 two longitudinal rows Fig. 35?. Nuclei of Cranial Nerves (Toldt). Motor 

 . . . red, sensory blue. The numbers correspond to 

 a median row, which the cranial nerves, 



consists of the nuclei of 



the third and fourth nerves in the floor of the aqueduct, and those 

 of the. sixth and twelfth nerves in the floor of the fourth ven- 

 tricle; and a lateral row comprising the motor nuclei of the fifth, 

 seventh, tenth, and eleventh nerves. The clumps of grey matter 

 which make up these nuclei may be considered as homologous with 

 the grey matter of the ventral or anterior (including the lateral) 

 horn of the spinal cord ; and the motor fibres of the nerves themselves 

 as homologous with the anterior spinal roots. Without going 

 further into the thorny subject of the homologies of the cranial and 



