1902.] " Blaze-currents " of the Crystalline Lens. 203 



unequalky good ; in three instances one of the lenses gave no response, 

 and in one of these three instances the eyeball was filled with blood. 

 I think the difference between the two eyes must have been due to the 

 fish having been killed by stunning, or it may be that in transit to 

 London one of the eyes had suffered compression. But whatever the 

 real cause of the difference may have been, the lenses of fish obtained 

 in London were far less satisfactory than those of fish directly taken 

 from the sea. In the latter case, both lenses, if carefully removed, were 

 equally effective (provided the fish had not been stunned in the usual 

 way on removal from the hook). 



Similar effects are obtainable on the crystalline lens of the mamma- 

 lian eye ; but it is essential to avoid any undue compression of the 

 globe. Thus I completely failed to observe any effect on the lens of 

 eyes removed from the orbit of dogs and cats in the usual manner, 

 also on the lens of sheep's eyeballs brought fresh from the slaughter- 

 house. 



But with lenses carefully removed from the eyes of a fresh sheep's 

 head and of a recently killed cat, typical and regular responses were 

 obtained, which were abolished by intentional compression as v T ell as 

 by immersion in hot water (60° to 70°). 



I think it desirable to give in extenso one experiment (No. 13) to 

 illustrate the precise nature of experimental evidence and the system 

 on which it is taken down. It is very easy to make sure of the 

 direction of a current used for excitation in relation to a total or 

 bipolar response, but it is not easy without a strictly systematic plan 

 to make sure of this relation when a partial or unipolar response is 

 under investigation. It is advisable for the latter purpose to carefully 

 verify the connections of the ABC key* so that directions of deflection 

 may immediately signify directions of current between the points of 

 investigation, and be noted accordingly in a legible form that can be 

 readily reviewed. 



Post. Equat. Ant. 



Exc. 5000 + through BA 

 Eesponse from AC 



Exc. 5000 - through BA 

 Eesponse from AC 



Exc. 5000+ through BA 

 Eesponse from BC 



Exc. 5000 + through BA 

 Eesponse from BC 



nit 



nib. 



—002 AnCi 

 post -kathodic, 



— -O04 Homo 

 post -anodic. 



* Described in "'Roy. Soc. Proc.,' vol. 69, p. 181. 



