THE INNERVATION OF THE LATERAL LINE SYSTEM OF 
AMPHIUMA. 
BY H. W. NORRIS. 
Kingsbury 1 has given us an account of the general distribution 
of the sense-organs of the lateral line system in Amphiuma. Ac- 
cording to him the arrangement in this form is almost typical of 
Amphibia. On the head : the supra-orbital group dorsal to the eye 
extends anteriorly to the tip of the snout; the infra-orbital group 
runs from the angle of the mouth ventral to the eye to the snout 
region; the oral line on the lower jaw passes along the lower lip; 
an angular series connects the oral with the infra-orbital ; the gular 
series is found on the ventral surface of the head extending from 
the branchial region to the tip of the lower jaw; a post-orbital 
series passes posteriorly from the infra-orbital to meet the gular in 
the posterior branchial region; a jugular connects the angular with 
the meeting point of the gular and post-orbital. On the trunk are 
three longitudinal series: a dorsal, a lateral or median, and a 
ventral line. 
This grouping of the sense-organs of the lateral line system in 
Amphiuma I find to correspond very closely to their innervation. 
As in Amphibia in general so in Amphiuma the lateral line organs 
are innervated by the so-called lateral line divisions of the seventh 
and tenth cranial nerves. The lateral line division of the seventh 
cranial nerve, the so-called “dorsal seventh,” arises from the me- 
dulla oblongata by three rootlets.. Of these the dorsal rootlet enters 
that portion of the medulla which in Necturus is designated by 
Kingsbury as the “dorsal island,” a mass of alba occupying the 
extreme dorsal part of the medulla. This dorsal island suggests 
an homology to the lateral line lobe (lobus lineae lateralis) of Cy- 
clostomes, Selachians and Ganoids, although Johnston 2 asserts that 
the lateral line lobe and the dorsal root of the dorsal VII are ab- 
sent in aquatic Amphibia. In the fishes mentioned the lateral line 
fibers of the seventh nerve distributed to the neuromasts of the 
1. Kingsbury, B. F. The Lateral Line System of Sense Organs in some American Am- 
phibia, and. Comparisons with Dipnoans. Proc. Amer. Micr. Soc., Vol. XVII, 1895. 
2. Johnston, J. B. The Nervous System of Vertebrates, Philadelphia, 1906. 
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