168 ANATOMY OF VERTEBRATES. 



mary set of nerves. The posterior or dorsal are usually the 

 smaller division, and, bending backward, soon subdivide into 

 external and internal branches. The pairs of nerves are classified, 

 according to the regions of the vertebral column where they 

 emerge, into ' cervical,' ' dorsal,' ( lumbar,' ( sacral,' ( caudal,' and 

 offer numerical differences corresponding with those of the verte- 

 brae, in the Mammalian series. Each is anterior to the correspond- 

 ing bony segment, and, for the most part, escapes between that 

 and the segment in advance ; but the notch of the c conjugational 

 foramen ' is always deepest at the fore part of the neurapophysis 

 answering to the nerve, and is directly perforated thereby in 

 many instances ; as, e. g. that of the atlas by the first cervical 

 in the Tapir, 1 and also that of the axis by the second cervical in 

 the Hyrax. 2 Most of the cervical and the dorsal vertebrae are 

 perforated by their corresponding nerves in the Hog and Pec- 

 cari ; 3 and some dorsals and lumbars are so perforated in most 

 Ruminants. 4 Therefore, I count the ' suboccipital ' nerve as the 

 first cervical one, and reckon the ( eighth cervical ' of Anthropo- 

 tomy as the ( first dorsal.' 



Some details of the distribution of the myelonal nerves in 

 Monotremata are given in Lxxxr. In the Cetacea they have been 

 described by Stannius 5 and Swan 6 in Phoccena communis. 



In the Porpoise, the first cervical has a distinct posterior root, 

 smaller than the anterior one, but with a small ganglion ; be- 

 yond which the two unite, as usual. The posterior or dorsal 

 branches supply the occipital and contiguous integument, and 

 the tegumentary and other muscles passing to the occiput ; 

 supplying, also, small branches to the ( masto-humeralis.' The 

 anterior or ventral branch passes along the scalenus, joins cor- 

 responding branches from the second and third cervicals, and, in 

 combination with the ' descendens noni,' supplies the sterno- 

 hyoid and sterno-thyroid muscles. The second and succeeding 

 cervical nerves are larger. A posterior branch of the second 

 perforates the masto-humeralis, and supplies the integument of 

 the neck. Other posterior branches of this and following cer- 

 vicals supply the interspinales, spinalis cervicis, splenitis capitis, 

 and the more superficial muscles and integument at the fore and 

 dorsal parts of the trunk : ventral branches go to the scalenus 

 anticus, levator anguli scapulas, and contiguous muscles. The 

 fourth cervical contributes the largest part of the ' phrenic nerve,' 

 but it receives a filament from the third cervical, sometimes from 

 the second ; always from the fifth. The left phrenic passes a 



1 xliv, p. 501. 2 lb. p. 522. 3 lb. pp. 543, 563. 



4 lb. p. 579. 5 lxxvi". LIT, 2d ed. p. 156. 



