202 



Dr. A. D. Waller. On the 



[Oct. 23, 



1000- -0-0080 



100+ -0-0003 



100- -0-0015 



After compression 1000+ and - nil, nil. 



Electrodes tested by 1000+ „ - „ ,, 



Note. — The lens of this fish is rather smaller than convenient. 

 Exp. 24. Frog. — E. temporaria. 



Entire eyeball. Initial current = - • 0030 



Exc. by single break 100+ = +off(>0-002) 



100- = +off(>0-002) 



Its isolated lens. 100+ and - = nil, nil. 



1000+ = -0-0005 



1000- = -0-0010 



Subsequently both responses were observed to be homodrome, viz., 

 + to + exc, and - to - exc. 



The isolated lens of the other eyeball gave similar results. 



The lens of the frog's eye is inconveniently small, nevertheless, with 

 due care, typical effects can be observed upon it, viz., negative 

 responses* to both directions of excitation, the homodrome exceeding 

 the antidrome response. The normal and typical response of the 

 entire eyeball was, as previously stated, positive to both directions of 

 excitation. Eana temporaria has, in my experience, given clearer 

 effects than Eana esculenta. 



Exp. 25. Cat. — 5 hours post mortem. 



1st lens. Initial current = -0-0030 



Exc. by single break 5000 + = — 0* 0005 



5000- = -off scale (> 0-0030) 



After compression the positive current was nearly doubled, and 

 there was no response to 5000 + 5000 - . 



The 2nd lens, less carefully removed, gave no response to 5000 + 

 and - . 



Of five successive cod's heads supplied to me in London as fresh, all 

 but one gave responses of typical character, as illustrated by the photo- 

 gram; in every case, however, the lenses of the two eyes were 



* Throughout this paper, positive current signifies current through the (eyeball 

 or) lens directed from posterior to anterior surface, and negative current the 

 reverse of this. In one experiment (Exp. 13, with reversed zincs) the direction of 

 the readings unavoidably breaks this conventional rule. And, indeed, in other 

 experiments this rule has occasionally been broken, as in Exp. 13, in order to set 

 aside conceivable fallacies of the electrodes, kept in an invariable relation to each 

 other — e.g., an invariable inequality between them, or a gravitation current of 

 liquid from A to B, or a constant difference of area, and therefore of current- 

 density at A and B. 



