NERVES OF MAMMALIA. 161 



with branches from the sympathetic to supply the complex 

 stomach and the numerous spleens. 



Most Mammals exhibit the grey enlargement of the vagus after 

 its exit from the jugular foramen, but less distinctly divided into 

 an upper, fig. 134, 6, and lower, ib. 18, ganglion, than in Man. 

 The principal branches — e.g. 7, auricular; 10, interganglionic ; 15, 

 pharyngeal, deriving one filament, 16, from the vagus, the other, 

 17, from the ( spinal accessory ; ' 19, 20, superior laryngeal, the re- 

 current, cardiac, pulmonary, oesophageal, and gastric — are the 

 same as in Man, likewise their connections with contiguous 

 nerves, and especially, as by the ' filaments,' 21, 22, with the upper 

 sympathetic ganglion. 



The spinal accessory, besides its portion, ib. 11, blending with 

 the trunk of the vagus, distributes branches to the trapezius, 

 masto-humeralis, and sterno-maxillaris, in Ungulates; to the 

 eleido-cucullaris and cleido-mastoideus, in Carnivores ; and to the 

 trapezius and sternomastoid in Quadrumanes and Man. The 

 condition of existence of a spinal accessory is not the extension 

 of muscles from the skull to the thorax for the acts of respiration, 

 but the general homology of the scapular arch as the haemal one 

 of the occiput : accordingly the nerve is found in all Vertebrates l ; 

 and only when the development of the appendage of that arch 

 calls for its displacement, and attracts for the manifold motive 

 and sensitive requirements of the limb, successive nerve-bundles 

 from the part of the myelon co-elongating with the neck, are the 

 root-filaments of the ' accessory ' drawn down beyond their 

 normal, intercranial, place of origin, as at 5, 5, fig. 134. 



The macromyelonal, by some called ( respiratory,' centres, to 

 which the origins of the several divisions of the ( eighth pair ' 

 have been traced, are connected by means of longitudinal fasciculi 

 and cell-columns, continuous with those in the cervico-dorsal 

 regions of the myelon, with the trigeminal nerves, and with both 

 anterior (lower and middle roots of the ' accessory') and posterior 

 cornua of the myelonal grey matter, fig. 40, g, h : thus minis- 

 tering to a series of motions, both direct and reflex, of high 

 importance. 



The roots of the ninth or hypoglossal nerve may be traced to 

 groups of nerve-cells in front of the central canal, ib. b, just 

 above the upper cervical nerves, apparently a continuation of the 

 cell-columns from which the ventral or motor roots of the spinal 

 nerves arise : some of the roots decussate at the raphe, but most 



1 For the homologue of this nerve, see, in Fishes, vol. i. p. 307 ; in Keptiles, ib. p. 

 313 ; in Birds, vol. ii. p. 125. 



VOL. III. M 



