MUSCLES, NERVES, AND ELECTRICAL ORGANS. 179 



/S-axis, the positive above and the negative below the plane. The 

 ordinates s themselves are not drawn, but the curves connecting 

 them corresponding to a definite density of current are drawn. 

 These therefore represent the strength of the secondary action due 

 to this density of current as a function of the time of closure. 

 Although these curves have similar courses they alter continually 

 with increasing density of current. They agree in the following 

 general characters. The zero time of closure corresponds naturally 

 to the zero of secondary action, consequently the curves themselves 

 start from the A-axis. Each curve rises quickly to a positive 

 maximum, and then sinks less rapidly but still very fast to the 

 ^-A-plane. These curves are drawn in the figure up to the point 

 where they intersect this plane as unbroken lines, beyond this 

 in their negative course they are represented by dotted lines. 

 Here appears a negative maximum which is generally less clearly 

 marked, and is at a greater distance from the point of intersection 

 than the positive maximum, though this distance diminishes with 

 increasing density of the current. Thus it occurs with I Daniell 

 only after 15', with I Grove after 10', with 2 Groves after 5', 

 with 5 Groves after i', &c. It lies at i' in the part of the table 

 shown, which was obtained with 10 Groves, and it is obvious that it 

 cannot depend at all on the weakening of the primary current by 

 secondary resistance. I have not followed the polarisation-curves 

 further than this negative maximum. However, they probably 

 present nothing particular, but approach very gradually the axis of 

 the times of closure, till from the excessive duration of the experiment 

 the results are obscured by all kinds of collateral actions. 



With a current density of less than 2 Groves and with a very short 

 time of closure there is generally no polarisation appreciable by the 

 galvanometer. The first traces observed with i Daniell and i" time 

 of closure, are negative ; internal polarisation of the muscle is also 

 obtained as I have long ago described, by passing a current com- 

 parable with its own for a long time through it 1 . The first positive 

 traces appear for the first time with 2 Groves and about o"3 time of 

 closure. 



The time of closure at which the positive polarisation passes 



into negative may be called the critical time. In the figure, 



the points at which the polarisation-curves described on the time 



of closure intersect the T-A-plane, are connected together by a 



curve drawn with an interrupted line. This curve is therefore 



1 Gesammelte Abhandlungen, vol. ii. pp. 191, 192. 



N 2, 



