ICO ANATOMY OF VERTEBRATES. 



organs the lungs and stomach which it supplies, sends branches 



^^ ^5 * J- 



also to the larynx, trachea, and heart. As in other Vertebrates, 

 it has the longest course, widest distribution, and most numerous 

 connections, of any of the cerebral nerves; but is noted, in Mam- 

 mals, by receiving the accessory nerve, ib. 5, 11,12, from a greater 

 extent of the myelon : the recurrent branches of the vagus are 

 more exclusively distributed to the trachea and larynx, and send 

 a smaller supply of nerves to the rcsophagus than in Birds or 

 Reptiles. 



From the remarkable length of the neck of the Giraffe, the 

 condition of the recurrent nerves attracted my attention in dis- 

 secting that animal : they were readily distinguishable at the 

 upper third of the trachea, but when sought for at their usual 



origin, this was less obvious. Each nerve was not due. as in the 



& ~ ' 



short-necked Mammals, to a single branch given off from the 

 vagus, continued of uniform diameter round the contiguous great 

 vessel and throughout their recurrent course, but it received 

 several small filaments derived from the trunk of the vagus at 



o 



different parts of its course along the neck. 1 Branches of the 

 superior laryngeal nerve directly perforated, as in some other 

 quadrupeds and in the Porpoise, the thyroid cartilage, and were 

 joined, in a greater proportion than in Man, by branches of the 

 recurrent, before distribution to the laryngeal muscles, of which, 

 however, the crico-thyroid owes its supply chiefly to the upper 

 laryngeal and the rest to the recurrents. In Quadrumana, as in 

 Man, the internal laryngeal perforates the thyrohyoid membrane 

 at the interval between the hyoid bone and thyroid cartilage. 

 The upper laryngeal is proportionally larger in the Orang, 

 Chimpanzee, and Gorilla, and mainly supplies the capacious 

 laryngeal sac in those apes. 



In the Porpoise the left recurrent winds round the end of the 

 arch of the aorta, near the remains of the ductus arteriosus ; 

 the right recurrent winds round the subclavian immediately 

 before the origin of the posterior thoracic : both recurrents send 

 filaments to the oesophageal plexus from the sympathetic on their 

 forward course to the larynx. After the origin of the recurrents, 

 the vagal trunk sends off the cardiac branch, which, unitino- with 



c5 



sympathetic filaments, forms the plexus supplying the heart. 

 Next are sent off the nerves to the bronchial plexuses ; finally 

 the vagal trunks pass with the rcsophagus through the diaphragm, 

 the left on the ventral, the right on the dorsal side, and combine 



1 xcvn'. 



