CONNECTOR NEURONS OF THE NERVOUS SYSTEM 137 



as Edinger suggests, some of the cells may be concerned with the 

 secondary or relay system of reflexes. 



There is another group of peripheral excitor neurons which 

 with their connector nerves belong to the mesosomatic group, 

 namely, the secretory neurons which give origin to the secretory 

 fibres of the parotid and submaxillary glands. According to 

 Kohnstamm, the cells which give origin to these nerve fibres form 

 two groups, the superior and inferior salivatory nuclei, situated 

 just dorsal to the facial nucleus and the nucleus ambiguus 

 respectively, and give the reflex path for direct simple salivary 

 reflexes. Close to these cells are found others which are the 

 end-nuclei of the sensory fibres of organs of taste, and are con- 

 nector neurons belonging not to a direct but to a relay system. 



The axons of the cells of the superior salivatory nucleus pass 

 into the nervus intermedius, and pass by way of the chorda 

 tympani to end in the cells of the submaxillary ganglia and the 

 other salivary ganglia belonging to the chorda tympani group. 

 The axons of the cells of the inferior salivatory nucleus pass 

 into the glossopharyngeal nerve and thence into the nervus tym- 

 panicus to end in the cells of the otic ganglion, which supplies 

 secretory fibres to the parotid gland (Fig. 6). Thus these cells 

 with their axons form the connector neurons between the secre- 

 tory neurons of the salivary glands and the appropriate sensory 

 neurons of the trigeminal, chorda tympani and glossopharyngeal. 

 They thus enable simple reflexes in the involuntary nervous 

 system to take place in these segments. 



CONNECTOR NEURONS OF THE PROSOMATIC REGION. 



The nucleus of the oculomotor nerve is a large nucleus made up 

 of a number of nuclei, each of which gives origin to one of the eye 

 muscle nerves. All these nuclei are composed of large cells, and 

 with their axons form the motor neurons of the voluntary muscles 

 belonging to the somatic segmentation in this region (Fig. 6). 

 Close against these cells but frontal to them and usually described 

 as part of the oculomotor nucleus, a well-defined group of cells is 

 seen, which are strikingly smaller than those in the rest of the 

 nucleus ; this small-celled group is believed to give origin to the 

 small fibres in the oculomotor nerve, which terminate in the ciliary 

 ganglion. Hensen and Volcker, in their original experiments, 

 mapped out by stimulation the different component parts of the 



