1902.] 



"Blaze-currents" of the Crystalline Lais. 



211 



BOA 



The first pair of ex- 

 citations is effective. 

 B is in each case the 

 seat of an ingoing- 

 response. 



The second pair of 

 excitations is ineffec- 

 tive. A has presum- 

 ably been exhausted 

 by previous excitation. 



Response of A is, 

 however, elicited by 

 tetanisation in both 

 pairs of directions. 



Exp. 30. Babbit's Eyes in situ. — A similar series of trials gave in each 

 case a small outgoing effect at each eye, presumably due to corneal 

 response. 



In tbe discussion, attention was drawn to the details of certain experiments — 

 viz., Exps. 3, 7, and 20 — as being in disagreement with the general rule that the 

 lens response is negative. Exps. No. 3 and 7 were made before I had learned the 

 importance of attending to the orientation of the lens. Exp. 20 (and Exp. 5) are 

 instances of what, in my experience, have presented themselves as transitional 

 types intermediate between the typical physiological response and the ordinary 

 polarisation effects of exhausted or dead organs. I have thought it possible that 

 certain irregularities of response occasionally met with might have been due to 

 unavoidable injury of the Retractor Lentis (Campanula Halleri), described and 

 figured by Beer.* 



After Exp. No. 7, I was always careful to mark the external or corneal pole of 

 the lens in situ by a speck of moist china clay, with which tbe clay end of 

 electrode A was subsequently brought into contact ; the opposite pole rested on 

 electrode B. 



I may take this opportunity of stating that the eyes of crabs and of lobsters 

 gave ingoing blaze-currents (from A to B) to both directions of excitation. 



S.S. 5000 + 

 5000 



5000 + 

 5000 



Tet. 5000 



b + 



Tet, 5000 



f m + 

 lb - 



+ 0-0004 

 + 0-0011 



nil. 

 nil. 



+ 0-0001 

 -0-0011 



0-0011 



* ' Pfliiger's Archiv,' vol. 58, p. 574. 



