552 yonrnal of Comparative Neurology and Psychology. 



and a second branch running similarly along the fourth branchial 

 arch and constituting a fifth ramus pretrematicus (prt. X. ^). The 

 main intestino-accessorius trunk finally divides (figs, i and 12) 

 into a r. lateralis ventralis supplying the ventral series of neuro- 

 masts of the trunk; three rr. intestinales that pass posteriorly, one 

 dorsal to the oesophagus and the other two latero-ventral to the 

 same; and a r. intestinalis recurrens that turns anteriorly to sup- 

 ply m. interbranchialis 4 (m. hyotrachealis) and mm. subarcuales. 

 From one of the intestinal branches there turns anteriorly a r. 

 laryngeus recurrens that innervates muscles of the larynx, mm. 

 dorso-laryngeus, constrictor laryngei, etc., and also supplies com- 

 munis fibers to the pharyngeal wall in the same region. Com- 

 munis fibers are also given oflF to the pharyngeal wall from the 

 r. intestinalis recurrens in the laryngeal region. The rr. intestinales 

 were traced posteriorly as far as the heart only and nothing can be 

 stated precisely of their destination. 



8. THE FIRST AND SECOND SPINAL NERVES. 



The first spinal nerve in its early stages, as described by Kings- 

 ley, arises by four roots, two dorsal and two ventral, and is thus 

 in origin clearly double (fig. 19). The common trunk formed by 

 these roots passes out through a foramen in the first vertebra. In 

 individuals of 120 mm. length I have found the first spinal nerve 

 to possess two very rudimentary dorsal roots, two large ventral 

 roots, and a small ganglion (fig. 19). In individuals of 140 mm. 

 length the dorsal roots have disappeared, but the ganglion remains. 

 In individuals of 175 m.m. length the ganglion has disappeared. 

 In older individuals the nerve appears to arise by four ventral 

 roots in two groups. According to Druner the hypobranchialis 

 (hypoglossus) nerve is derived from the first and second spinal 

 nerves. Careful search through my preparations fails to show 

 any anastomosing between these two nerves. I have found no 

 instance where they come into contact even. The nearest approach 

 to contact is between a general cutaneous division of the second 

 spinal nerve and the main hypoglossal trunk of the first spinal 

 nerve. The hypoglossus nerve is formed solely from the first 

 spinal nerve, and contains only motor fibers. The main ventral 

 portion of the first spinal nerve soon after it emerges from the 

 spinal canal passes posteriorly and after giving off a few small 



