480 



Dr. A. D. Waller. 



Plate 6. 



E. Xanthophylls obtained from an extract of Ficus Repens in the month of 



May :— 



(1) Chrysophyll obtained from the crude solution of the xanthophylls. 



(2) Crude solution of the xantbophylls. 



(3) A mixture of chrysophyll and the alcoholic portion. 



(4 and 5) The alcoholic portion of different strengths, showing a slight 

 obscuration. 



F. Xanthophylls obtained from an extract of Ficus Hepens in the month of 



December: — 



(1) Crude solution of the xanthophylls ; a case in which the fourth band 



is almost, if not, absent. 

 (2 and 3) The alcoholic portion of different strengths. This is the usual 



appearance of this spectrum, showing the bands more or less 



obscured. 



(4) The alcoholic portion after standing a little time, the spectrum being 



the same as that produced immediately by the action of HC1. 



G-. The action of HC1 on the xanthophylls : — 



(1) The first CS 2 fraction. 



(2) The first CS 2 fraction + HC1. 



(3) Crude solution of the xanthophylls. , 



(4) Crude solution of the xanthophylls + HCL 



(5) Alcoholic portion (F - 2) + HC1. 



" On Skin Currents. — Part I. The Frog's Skin." By Augustus 

 D. Waller, M.D, E.E.S. Eeceivecl May 29 — Eeacl June 6, 

 1901. 



The principal object of the following observations was to investigate 

 in the case of skin an electrical reaction by which it is in general 

 possible to determine whether an animal or vegetable tissue is alive or 

 dead.* 



A side issue raised in connection with the general inquiry was 

 whether or no the test is applicable to the human body ; this obviously 

 led to a detailed study of skin effects upon man and upon animals. 



In the case of the frog, previous observations on skin currents are 

 numerous and conflicting ; but in so far as my present theme is con- 

 cerned, the results have come out with the utmost regularity and quite 

 clear of any suspicion of physical fallacy. In the case of man, the 

 question has proved to be less simple, and although it is easy to dis- 

 tinguish between an assuredly living and an assuredly dead piece of 

 skin, it is far from easy in doubtful cases to make sure that the skin 

 is completely dead. The difficulty is caused by polarisation currents 



* ' Roy. Soc. Proc./ yoI. 68, p. 79. References to previous papers are git en 

 there— p. 92. 



