502 ANNALS NEW YORK ACADEMY OF SCIENCES 



were carefully isolated, and transverse slices about 1 millimeter thick 

 cut out with fine scissors. Such fragments contain 10 to 20 plates, 

 many of them damaged by the dissection. The intact ones retain a 

 good excitability for hours. By transverse electrical stimulation at 

 threshold values, it is sometimes possible to record responses which, be- 

 yond all doubt, are elementary (plate 4A, lower record). They obey 

 the all-or-nothing law and are the conspicuous components of the com- 

 plex waves obtained with slightly higher intensities. In Torpedo, they 

 last 1.75-2.25 msec, (rising phase, 0.5-0.7 msec.) ; in skates (Auger and 

 Fessard^), they are much longer, about 12 msec, (rising phase, 2-2.5 

 msec). Now the discharge of a whole column is noticeably of longer 

 duration (plate 4A, middle record). In spite of the shortness of the 

 nervous tracts contained in these small pieces of tissue, latencies vary, 

 from less than 1 msec, to more than 4 msec, and dispersion of com- 

 ponents lengthens the wave duration to 2 or 3 times its elementary 

 value. The natural discharge starting off the whole organ is hardly 

 longer. The long distance command is transmitted by high velocity 

 fibers of large diameter, and these do not introduce such an important 

 shift in components as do the thin nerve branches at the periphery. 

 The elementary electrical process is, therefore, comparable to a nerve 

 action potential, never being diphasic, as conduction is absent. Posi- 

 tive after-potentials have never been observed. Mention must be made 

 of some variations in the declining phase, which is sometimes longer 

 than usual, especially in skates. In these cases, the discharge is more 

 like an end-plate potential than an action potential. 



B. The analogy between the electric organs and other excitable 

 systems retains its value when the electrical conductivity is studied 

 during the discharge. Using the impedance bridge method, applied by 

 Cole and Curtis^^ to the squid giant axon, we have observed^ a transient 

 drop of impedance during the activity of Torpedo and Raia organs. 

 Recently, Cox, Coates, and Brown^^ have obtained indirect evidence 

 of a diminution in ohmic resistance during the discharge of Electroph- 

 orus electricus. 



Plate 4B shows one of our records obtained with a double beam 

 cathode ray oscillograph. The upper record is the discharge of an 

 isolated column {Raia), placed in one branch of an impedance bridge; 

 the lower one shows the reappearance of the 15,000 cycles oscillation 

 feeding the bridge. The two phenomena start simultaneously, instead 

 of showing a shift as in the nerve, a fact easily interpreted as a lack of 

 conduction The impedance change is slight, less than 10 per cent, but 



