ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
623 
ventral and two dorsal. Each is roughly shaped like a three-sided prism 
with tapering conical ends, and is invested with a tendinous sheath. 
Connected with this sheath are numerous vertical connective-tissue 
partitions which divide the organ into a series of compartments, within 
which lie the electric plates. The number of these seems to be more or 
less constant for the species, the growth of the organs being due to an 
increase in the size of the plates and not to an increase in number. The 
plates are separated from the partitions by a layer of mucoid tissue in 
which the nerves ramify. In some species the nerves penetrate the plate 
in front and in some behind ; there is also variation in the number of the 
branches into which the nerve breaks up. As to the difficult point of 
the relation between the myelin threads and the pale nerve-fibres, the 
author finds that the dark fibres consist of 30-50 myelin threads, which 
invest like “ a finger-stall ” the conical origin of the pale fibres. The 
latter consist of (1) a connective-tissue sheath with spindle-shaped 
nucleated cells, beneath which lies (2) a thin nucleated membrane, the 
electrolemma, then (3) a thick homogeneous sheath surrounding (4) the 
central axis-cylinder. In considering the connection between the fine 
branches of these nerve-fibres and the electric plates, it is first necessary 
to consider the structure of the latter. Each consists of three layers, 
an anterior and a posterior layer of similar structure, and a central layer. 
Each outer layer consists of a homogeneous mass finely dotted and con- 
taining oval nuclei. Under high magnification it is seen that the dotted 
appearance is due to minute fibrillar rods, perpendicular to the surface 
of the plate, and probably representing the remains of muscle-fibres ; 
they are connected with the swollen ends of the pale nerve-fibres. The 
middle layer of the plate consists of striped muscle-fibres, though, owing to 
the extreme rapidity with which they undergo change, this is not always 
easy to demonstrate. They are surrounded by a transparent substance. 
Finally, as to the relation of the pale nerve-fibres and the plates. 
Where the connective-tissue sheath persists (as in M. oxyrhynchus ) to 
their branched ends, it is continued into the mucoid layer between the 
plates. The thin electrolemma beneath it spreads out over the surface 
of the plate, the thick sheath of the fibre is continuous with the trans- 
parent layer of the plate. The fate of the axial cylinder is unknown, its 
fibrils have been followed only to the end of the little rods. 
Toxin and Anti-toxin of Snake-venom.* — Dr. Charles J. Martin 
has been continuing his observations on this subject, with especial re- 
ference to the observed discrepancy between the quantities of auti- 
venene required to neutralise a given dose of venom, when they are 
(1) previously mixed outside the body; and (2) simultaneously injected 
under the skin. His conclusions are that (1) about the same quantity 
of anti-venene necessary to neutralise the venom in vitro is capable of 
doing so when the former is injected into the blood-stream, and the 
latter sub-cutaneously ; (2) at least ten to twenty times this quantity is 
required when they are both placed simultaneously under the skin, but 
in different parts of the body. The author is of opinion that these 
results markedly support his view that the nature of the antagonism 
between the toxin and anti-toxin is a chemical one. The practical 
result is that the anti-venene should be injected intravenously. 
* Proc. Roy. Soc. Lend,, lxiv. (1898) pp. 88-94. 
2 u 
1898 
