ELECTRIC TISSUES IO/ 



or intestine. Others are found scattered sparingly through the middle 

 layer. The middle or striated layer represents the striated body of the 

 striated muscle fiber in which the prominent lamellae of muscle units 

 are more or less absent. In some of the most powerful and efficient 

 electric organs this middle layer is apparently missing, leaving only 

 parts, the electric network, which exists between the lamellae in less 

 specialized forms and also may exist in normal striated muscle cells. 

 A thin membrane surrounds the whole syncytium and is called the 

 electrolemma. 



The specific cell-organ through the action of which electricity is dis- 

 charged is probably a series of fine rod-like structures attached to the 

 electrolemma and directed towards the anterior layer on which they rest. 

 They have not been actually described as present in all electric tissues, 

 but are probably so present. They are exceedingly small and in some 

 forms are straight and simple, and in others are curved and provided 

 with peculiar end -knobs, and sometimes are combined into groups of 

 two or three. 



These electric rods are sometimes found all over the surface of the 

 electrolemma ; in other cases they occur only at, or near, such points of 

 it as are touched by the end-plates of the nerve that supplies it. 



While the electric rods are probably the means through which the 

 electricity is discharged, there should be another cell-organ by which it 

 is stored up in some potential form through nutritive processes. A 

 protoplasmic network of fine, irregular fibers in which granules are 

 embedded has been surmised, in Raja and other forms, to be such an 

 organ. This network pervades the entire electroplax more or less, 

 being found between the lamellae only of the striated layer when these 

 lamellae are present. This network probably acts as an area of deposit 

 for the numerous granules that are secreted by the cytoplasm. We shall 

 call such granules the electrochondria, as they are probably homologous 

 to the myochondria of the muscle cell, and used to produce electricity 

 by some chemical process. 



The nerve supply enters the compartment, usually from an anterior 

 corner, as one or more medullated fibers derived from the electric nerve, 

 which is a modified motor nerve. These fibers lose their medullary sheath 

 soon after entering the compartment, and branch and rebranch until 

 they touch the electroplax at many points and spread out into the end- 

 plates. These nerve end-plates form an irregular but characteristic 

 network that covers most of the electric surface of the electroplax. This 

 area of contact between nerve and electroplax is reduced to a number 

 of evaginated points in Gymnotus, the electric eel ; to still fewer in Mor- 

 myrus, and to one point in Malapterurus, the electric catfish. 



The rays, Raja, present an electroplax in which the general features 



