410 ELECTRO-PHYSIOLOGY CHAP. 



through a ganglionic complex, e.g. spinal cord, may be comparatively 

 protracted. It is obvious that the shock will be sharper, more 

 stinging, and more acute, in proportion as the discharge from the 

 plates occurs more simultaneously." The effect, moreover, differs 

 according to the part at which the Torpedo shock takes action. 

 Schonlein experienced pain on receiving it on the back of the 

 fingers and hand, while in the palm of the hand it is a mere 

 " pricking " sensation. In artificial excitation with induction 

 currents the feeling of contraction in the muscles of the hand 

 may always be distinguished from the cutaneous sensations. 

 According to Schonlein this never occurs in the shock of 

 Torpedo; the discharge must therefore be inadequate to excite 

 the muscles beneath the skin. Faraday compared a medium 

 shock from the electric eel 101'G cm. long, on which he experi- 

 mented in 1838, with the discharge of a Leyden battery, charged 

 to the maximum with fifteen jars, and a double-glazed glass 

 surface of 2 '2 5 8 sq. m. The physiological action of the Torpedo 

 discharge is disproportionately weaker, with the exception of the 

 large species (T. occidentalis), by the shock of which Captain Atwood 

 was repeatedly thrown to the ground, " as if felled by an axe." 



In order more exactly to investigate the action, strength, and 

 direction of the discharge from a fish still in water, Faraday 

 employed a pair of saddle-shaped, curved electrodes (Fig. 266) for 

 Gymnotus, invested internally with metallic, externally with in- 

 sulating substances. These were applied to two points, correspond- 

 ing with the poles of the organ, of the fish, lying upon an insulating- 

 stage (glass plate), which again was gripped by the gutta-percha 

 rim of the saddle. The segments of the fish are then almost as well 

 insulated as if they were in the air. It is best only to leave as 

 much water as just covers the animal when lying upon the glass floor 

 of a shallow trough. In order as perfectly as possible to insulate 

 the part of the body gripped by the saddle in the smaller and 

 weaker Malapterurus, du Bois-Keymond made use of a cover for 

 leading off, shaped like the lid of a mummy-case (Fig. 26V). This 

 was moulded in gutta-percha to the shape of the animal, the ends 

 being lined with tinfoil (4 r/, ii. p. (>70). 



The insulation from the surrounding water was in this 

 instance so complete that even the very delicate method of 

 testing for current escape in water (to be described below) failed 

 to detect any at the time of the discharge. Du Bois-Eeymond 



