THE SO-CALLED DORSOTRACHEALIS BRANCH OF 
THE SEVENTH CRANIAL NERVE IN AMPHIUMA. 
BY H. W. NORRIS. 
Fischer in his work on the Derotremes and Perenni- 
branchs* describes a peculiar branch of the seventh cranial 
nerve in Amphiuma, distributed, according to his state- 
ment, to the hyotrachealis muscle. Kingsley in his recent 
paper on the cranial nerves of Amphiumaf agrees with 
Fischer that the nerve is one having no homologue in 
other Amphibians. According to him the nerve ends in 
the dorsotrachealis muscle. My own observations are so 
at variance with the views of these two writers that the 
following detailed account of the course of this extraordi- 
nary nerve is hereby given. Observations were made upon 
specimens of Amphiuma at different stages. A projection 
of the cranial nerves of a 130 mm. specimen w^as made by 
plotting of serial sections. (See accompanying illustra- 
tion.) While the material had been neither preserved 
nor stained with a view to tracing nerve components, yet 
it gave results far better than was to be expected. 
As Kingsley says, there emerge on the posterior surface 
of the hyomandibular trunk of the seventh cranial nerve 
four branches. The first is Jacobson’s commissure, pass- 
ing posteriorly and dorsally to anastomose with the glosso- 
pharyngeal nerve. The fourth branch, or hyomandibular 
proper, arises as two branches or as one that immediately 
divides into two. The second and third branches immedi- 
- * Fischer, J. G. — -Anatomische Abhandlun gen uber die Perennibranchiaten und 
Derotremen. Hamburg, 1864. 
+ Kingsley, J. S. — The Cranial Nerves of Amphiuma. Tuft’s College Studies, No. 
7, 1902. 
•J (95) . 
