370 ELECTRO-PHYSIOLOGY CHAP. 



organ. Fine septa, parallel with the plane of the cross-section 

 (" transverse partition walls "), produce from the lateral aspect a 

 delicate cross-striation of the single prisms, and divide them into 

 closely-compressed narrow compartments, in each of which an 

 " electrical plate " is supported at right angles. The form of this 

 compartment, and of the plate within it, may in general be 

 described as rectangular, with greater or less diminution towards 

 the centre. 



The average width of the compartments in the organ of 

 Gymnotus is about ^ mm., agreeing with the older observations 

 of Hunter, who reckoned about 240 transverse septa to the 

 English inch, i.e. about 0'1058 mm. width of compartment. In 

 Torpedo it is about ^ mm. The distance between the two 

 longitudinal septa (height of compartment) is of course much 

 greater. It is about 0'64 mm. in Gymnotus (Hunter). The total 



FIG. 239. 



number of compartments lying between two longitudinal partition 

 walls, with the band-shaped plates which they contain, may again 

 be described as " columns," analogous with the prismatic columns 

 standing at right angles to the body superficies in the organ 

 of Torpedo. The columns of the large organ spring collectively 

 (as shown by the lateral schema, Fig. 239) from behind and 

 below the intermediate muscular layer, and ascend at a sharp 

 angle above and in front. Only the foremost run approximately 

 parallel with the axis of the fish. 



Even to the unaided eye a certain part of the two large 

 organs exhibits peculiar characteristics ; i.e. it is darker, more 

 transparent, and of a yellow-gray or pinkish colour, instead of 

 being white like alabaster. This is because (as Pacini, 25, showed, 

 Fig. 240, a, b) there are, along with the ordinary columns with 

 small compartments, others in which the spaces are very wide. 

 Sachs confirmed these observations. The " Sachs' bundle of 

 columns," which he was inclined to regard as a new electrical 

 organ in Gymnotus, lies as a rule above the posterior half 

 of the large organ. It begins anteriorly in a fine point 



