238 SUMMARY. 



of its branches, is larger, according to the extent of the parts to be supplied ; it 



gives off one or more lateral or dorsal branches in fishes ; in mammalia, the external 



and superior laryngeal and recurrent nerves are similar to those in man, but their 



branches are rather more combined before their termination ; in the jaguar, the 



superior laryngeal as well as a minute branch of the external laryngeal pass through 



separate foramina in the thyroid cartilage; the recurrent nerves differ in birds and 



amphibia from those of mammalia in supplying the oesophagus in a greater degree 



than the larynx. In fishes, a recurrent branch also exists, which winds round one of 



the branchial arteries to supply a muscle connected with the motion of the gills ; the 



pulmonary branches are similar in the four superior classes, but are destined for the 



gills in fishes instead of the lungs in others. The cardiac plexus is formed of the 



sympathetic, par vagum, and recurrent in mammalia : it is more complicated in man ; 



it is similar in birds ; in amphibia it is formed more of branches of the par vagum ; in 



fishes, its state has not been determined. The par vagum supplies the stomach in the 



four superior classes, the branch connected with the coeliac plexus for keeping all the 



small intestines and the beginning of the colon under the influence of the brain exists 



throughout mammalia ; a communication between a branch of the par vagum and the 



coeliac and splanchnic nerves exists in birds ; in the snake, communications also exist ; 



in fishes there are also some. The ninth exists in the three superior .classes, in man 



it arises from the continuation downwards of the oblique tract of the annular tubercle, 



and in mammalia from that of the trapezoid body ; it supplies the muscles of the 



tongue and others connected with the hyoid bone and thyroid cartilage. In some 



birds, as the goose and turtle, it resembles very much that in mammalia, but in others, 



as the pelican, crane, and snake, the glosso-pharyngeal, par vagum, and ninth are so 



conjoined, that it is very difficult to determine the destination of each. The accessory 



nerve exists in man and mammalia ; in birds, it is not present, unless the lengthened 



origin of the par vagum may be considered as a part of it ; in some of amphibia it 



may be seen, as in the turtle, but not in fishes. 



The spinal cord is nearly the same in the four superior classes ; in the inverte- 

 brate there is a cord or ring in the place of it, analogous to its nerves and ganglia ; 



