1092 
SCANDINAVIAN FISHES. 
dorsal side, one pair on the outside of the preorbital 
cartilage (oa) and another outside the spiracle ( liya :). 
Asymmetrical capsules also occur, as in Trygon between 
the anterior ends of the two nostrils. The ampullary 
canals extend throughout the sides of the body, those 
of the pectoral fins for example, which run to the 
hyoid capsules, attaining a considerable length (fig. 309). 
In the Electric Rays Fritsch" has observed a regular 
alternation on the dorsal side of the pectoral fins be- 
tween the ducts of the ampullae and those of the lateral 
canal proper, the outer (distal) part and the orifice of 
each ampullary duct lying as a rule between a pair of 
the outward transverse branches of the lateral line. 
To this he appends the remark that the presence of 
Fig. 309. Hyoid ampulla and their opening ducts together with the 
dorsal course of the lateral line in the left half of a Raja. 
After Garman. 
true sensory bulbs (nerve-bulbs) with the hair cells 
occurring in the lateral line has not yet been demon- 
strated in the nerve ends on the inner trail of the 
ampullae, whence he infers that the ampullae should 
be regarded as a secretory part of the system of the 
lateral line. Their cavity is filled with an endolymph- 
like, more or less coagulated mucus. 
The third kind of organs belonging to this system, 
the so-called sensory vesicles of SavE, appear only in 
the Electric Rays, and are situated in one or two series 
on the snout of these fishes and around the anterior 
part of their electric organs. They are homologous 
with the carnal bottoms of the ampulla:, but are entirely 
closed, and their inner surface is usually furnished with 
three sensory spots, the middle spot being the largest 
and furnished with numerous hair cells. 
The fourth kind (fig. 308, po) of the sense organs 
now under consideration are the so-called pit organs c 
(called by FritsciE spalt-papillen). These are present 
in our common Rays, and are wart-like dermal growths, 
open at the top and containing a spherical or some- 
what more prolongated (bottle-shaped) cavity, which is 
filled with sensory cells furnished Avith hair-like pro- 
cesses and surrounded by supporting cells. The pit 
organs or sensory follicles lie scattered in toavs along 
the inferior orbital margins, in the temporal region, 
and on each side of the median line of the body, be- 
tAveen this and the true lateral line. 
The innervation of the entire system of the lateral 
line is supplied, according to Eavart, almost exclusively 
from branches of the facial nerve * 6 and from the late- 
ralis. The supraorbital branch (fig. 308, 1 — 6) and the 
rostral ampullae ( Ha) are supplied by the superficial 
ophthalmic division of the facial, the suborbital branch 
and the anterior part of the occipital, the orbital am- 
pullae (oa), and the pit organs (po) at the orbits by the 
buccal division of the facial, and the hyomandibular 
branch (12 — 19) together Avith the hyoid ampullae (hi/ a) 
and the mandibular branch (27) b} r the hyomandibular 
division of the facial nerve. The lateral line proper, 
as Avell as the posterior part of the occipital branch, 
the transverse occipital canal (21), and the majority of 
the pit organs (po), is innervated by the lateralis, one 
of the main divisions of the vagus. 
As Fritsch has remarked, some obscurity still 
obtains in the question of the physiological importance 
of the entire system of the lateral line; and the division 
a Die Elelctrischen Fische, II, p. 87. 
6 Matteucci and Saa’i, Traite des phe'nomenes electrophysiologiques des animaux, Paris 1844. 
c Trans. Roy. Soc. Edinb., vol. XXXVII (1891 — 92), p. 101. 
J Stzber. Akad. AViss. Berk, VIII (1888), p. 291. 
e This nerve consequently consists in fishes, according to Ewart, of both sensory and motor fibres. In the higher vertebrates it is 
motor alone, the sensorial parts, according to Ewart, having disappeared. According to the older opinion, which is no doubt still maintained 
by the majority of anatomists, the divisions enumerated above belong to the trigeminal group. 
