. Animal physiology. Physiology, Comparative. 344 BTRUCTURE AND ACTIONS OF ELECTRIC ORGANS. organs of the Gymnotus are essentially the same in structure, hut differ in shape in accordance mth the conformation of the anhnal; they occupy one-third of its whole bulk, and run nearly along its entire length, being arranged in two distinct pairs, one much larger than the other. In the Malapterurus. (fig. 179), there is not any electrical organ so definite as those just described; but the thick layer of dense areolar tissue which completely surrounds the body, appears to be sub- servient to tliis fun
. Animal physiology. Physiology, Comparative. 344 BTRUCTURE AND ACTIONS OF ELECTRIC ORGANS. organs of the Gymnotus are essentially the same in structure, hut differ in shape in accordance mth the conformation of the anhnal; they occupy one-third of its whole bulk, and run nearly along its entire length, being arranged in two distinct pairs, one much larger than the other. In the Malapterurus. (fig. 179), there is not any electrical organ so definite as those just described; but the thick layer of dense areolar tissue which completely surrounds the body, appears to be sub- servient to tliis function ; being composed of tendinous fibres interwoven together, and containing a gelatinous substance in its interstices, so as to bear a close analogy with the special organs of the Torpedo and Gymnotus. 423. In aU these instances, the electrical organs are sup- plied with nerves of very great size, larger than any others in the same anmials, and larger than any nerves in other animals of like bulk. These nerves arise from the top of the spinal cord, and seem analogous to the pneumogastric nerve (§ 458) of other animals. The influence of these nerves is essential to the action of the electric organs. If all the trunks on one side be cut, the power of the corresponding organ will be destroyed, but that of the other may remain uninjured. If the nerves be partiaUy destroyed on either or both sides, the power is retained by the portions of the organs which are still connected with the brain by the trunks that remain. Even slices of the organ entirely separated from the body, except by a nervous fibre, may exhibit electrical properties. Discharges may be produced by irritating the part of the nervous centres from which the trunks proceed (so long, at least, as they are entire), or by irritating the trunks themselves. In all these respects, there is a strong analogy between the action of the nerves on the electric organs and on the muscles (Chap, xii.) ; and it may be safely affirm
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