664 SYMPATHETIC AND OTHER SYSTEMS OF NERVES. 



vagi. In the cat I have made a similar experiment, and come to the same 

 result as regards the fibres to the oesophagus (lower cervical and thoracic 

 portion), the stomach, the intestines, and heart. 



We may conclude that the autonomic fibres of the vagus end in 

 connection with peripheral nerve cells, since in the rabbit a small dose 

 of nicotin prevents any effects being obtained by stimulating the nerve 

 in the neck. It is probable that the nerve fibres for each organ end in 

 small ganglia situated in or near the organ itself. This is shown, as 

 regards the cardiac inhibitory fibres in the mammal and frog, by the 

 continued inhibitory power of muscarin, after nicotin injection ; and 

 in the frog, also, by the inhibition obtained by local stimulation after 

 injection of nicotin. 



Twelfth nerve. — The peripheral part of the hypoglossal nerve has 

 a slight vaso-constrictor action upon the arteries of the tongue. The 

 vaso-constrictor fibres come in part, at any rate, from the superior 

 cervical ganglion. It has been supposed that some issue with the roots 

 of the hypoglossal nerve, but the evidence is not satisfactory. In some 

 animals the hypoglossal nerve has constantly, in others occasionally, 

 a small gangliated root ; the ganglion is apparently homologous with 

 the jugular ganglion, i.e. it belongs to the system of spinal ganglia, and 

 not to that of the autonomic ganglia. 



Characters of the cranial autonomic nerve fibres. — The nerve 

 strand running from the third nerve to the ciliary ganglion consists 

 chiefly of small medullated fibres. The fibres proceeding from the 

 ganglion also consist chiefly of small medullated fibres ; they are three 

 to four times as numerous as the fibres running to the ganglion. These 

 facts were pointed out by Bidder and Volkmann 1 in 1842. 



The chorda tympani, Jacobson's nerve, the superficial petrosals, 

 have very few medium or large fibres. 



One or two medium or large fibres usually run to the submaxillary gland — 

 sometimes branching as they go — by way of the duct ; the chorda tympani, 

 after leaving the lingual, has usually no fibre larger than 3*5 /x ; in the 

 tympanic cavity it has more medium and large fibres. 



The post-ganglionic fibres of the otic, spheno-palatine, and sub- 

 maxillary ganglion are chiefly, at any rate, non-medullated. The 

 nerve cells on the course of the cranial nerves so far considered have the 

 same general characters as those of the sympathetic system. 



The vagus at its exit from the skull contains many large fibres, as 

 well as many small ones. The large fibres pass off chiefly to the 

 pharynx and larynx. The branches of the nerve which run to the 

 oesophagus and to the stomach consist of non-medullated fibres, small 

 medullated fibres, a considerable number of medium, and hardly any 

 large fibres. The branches to the lungs contain more large fibres than 

 those to the oesophagus and stomach. 



Bidder and Volkmann 2 give the proportion of small to large fibres in the 

 branches of the vagus of the cat as follows : — In the superior laryngeal, 2:1; 

 in the inferior laryngeal, 1:8; in the branches to the lungs, about 2:1; in 

 the branches to the oesophagus and stomach, hundreds of small, and hardly 

 any large, with much ' Zellgewebe,' i.e. Remak's fibres. 



1 " Die Selbststandigkeit des sympathisehen Nervensystems," Leipzig, 1842. 

 - Op. tit., S. 62. 



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