viii.] A LIMITATION 141 



lutely that any given object exhibits no blaze at all. The 

 internal organs certainly do not blaze like the skin, or even like 

 nerve, the failure is in itself of interest, and the cause of differ- 

 ence matter for investigation, and we shall have to learn what is 

 the determinant factor between a living tissue that manifests 

 blaze, and another living tissue that does not. Durig thinks 

 that the effect is peculiar to epithelial tissues, and it is certainly 

 the case that epithelial tissues do give it better than other 

 tissues witness the case of the crystalline lens. But I do 

 not think it is confined to epithelia, for it occurs in muscle, 

 and in vegetable tissues which can scarcely be classed as 

 epithelial. 



I am unwilling to express any opinion at all. I have 

 witnessed it in muscle ; witnessed it in some frog's spawn, 

 and failed to witness it in other frog's spawn. Does it depend 

 upon some regular orientation of cells? Is their regular 

 arrangement on a basement membrane a favouring condition 

 of things? What part do membranes play in the effect? 

 These are questions all of which I must leave unanswered 

 now. 



In two successive years I took occasion to examine seaweeds, 

 with the object of comparing their reactions with those of land 

 plants. To my considerable surprise, they gave little or no 

 reaction, and I left the seaside on the first occasion without 

 having been able to satisfy myself of the physiological nature of 

 such small reactions as were occasionally witnessed. The " weeds " 

 obtained in the Channel Islands in an obviously living state 

 during the month of August always gave small antidrome 

 after-currents at both poles to single shocks as if by ordinary 

 polarisation. But the effects were abolished by boiling. This 

 was a puzzle, and I cannot yet explain it. The elements of 

 the problem are : deflections antidrome throughout, therefore 

 apparently ordinary polarisation ; but abolished by boiling, 

 therefore apparently of a physiological character. 



Pieces of apple gave a similar puzzle, viz., antidrome effects 

 abolished by boiling, and it is possible in such cases that we 

 have to do with a mere physical effect of altered structure or 

 altered composition, possessing no physiological significance. 



