272 
DR. DAVY’S ACCOUNT OF SOME EXPERIMENTS 
electricity, the margin of the pectoral fins has acquired an appearance as if 
very minute bubbles of air were generated in it and confined. 
Besides the electrical nerves there is a plexus of nerves deserving attention, 
of great magnitude, formed by the junction of the anterior and posterior, or 
upper and under cervical nerves ; of the former about seventeen on each side, 
of the latter about fourteen *. It makes its appearance as one trunk just 
below the transverse cartilage which is interposed between the thorax and ab- 
domen. It sends a recurrent branch to the muscles and skin of the under 
surface of the thorax ; but its main trunk ascends along the inner margin of 
the pectoral fin, and is distributed through it. On this plexus the sentient 
and motive powers of the parts connected with the electrical organs seem to 
depend. 
The electrical nerves at their origin are enveloped in a very thick fibrous 
sheath. As the branches subdivide in the substance of the organ, the neuri- 
lema becomes thin and semitransparent. On examining a minute branch with 
a powerful lens, its internal or medullary substance is not seen in a continuous 
line, but interrupted, as it were dotted, as if the sheath contained a succession 
of portions with a little space between each. 
In the anatomical structure of the torpedo, the mucous system forms a very 
conspicuous part; it consists of several clusters and chains of glands distri- 
buted chiefly around the electrical organs, at different depths beneath the cutis ; 
and of strong transparent vessels, of various lengths and sizes, opening exter- 
nally in the skin, for the purpose of pouring out the thick mucus secreted by 
the glands, and destined for lubricating the surface. This system has not 
been noticed by Mr. Hunter, and it has been but imperfectly described by 
Lorenzini -j~. Though it is not peculiar to the torpedo, it is much more strongly 
developed in this fish than in any other species of Ray with which I am ac- 
quainted, and the situation of the glands and the distribution of their vessels 
are different. Whether it is concerned in any way with the electrical function 
of the torpedo is deserving of consideration. That it is thus concerned in some 
' Towards the origin of the spinal cord there is a small space, from the under surface of which six 
nerves arise, three on each side ; but none from the upper surface, whence the difference of number 
noticed in the text. 
| Osservazioni intomo alle Torpedini fatte daSxEFFANO Lorenzini Fiorentino ; 4to, Firenze, 1G78. 
