1902.] "Blaze-currents" of the Incubated Hen's Egg. 187 



shocks at intervals of 5 or 6 minutes. By strong tetanisation the 

 reaction is completely abolished ; the chick has been " electrocuted." 



In a third series of ten trials upon "fresh eggs" from a London 

 shop, and at a very unfavourable time of year as regards develop- 

 ment, the results were as clear as could be desired. At the end of 

 12 days of incubation nine of these eggs returned what was by this 

 time familiar to me as a negative answer, viz., small counter-currents 

 due to polarisation, and all the nine showed no sign of development ; 

 only a single egg gave blaze-currents of ±0*0010 volt, and was found 

 to have developed to the extent usual at the end of 24 hours under 

 ordinarily favourable conditions. 



In the following year (1902) I returned to the subject and made 

 two further series of observations, paying particular attention to the 

 direction of blaze-currents of the first few days of incubation. In the 

 interval between these observations and those of the previous year I 

 had studied the currents of mucous membranes, with the general, but 

 by no means invariable, result that the blaze-currents are of ingoing 

 direction. I therefore expected to find, and did find, that the response 

 of an early blastoderm to either direction of current is of positive or 

 ascending direction, i.e., ingoing as regards the hypoblast, and out- 

 going as regards the epiblast. 



I also took the opportunity of testing active eggs on what has been 

 described in previous papers* as the ABC plan, i.e., after excitation 

 through A, the superior pole, and B, the inferior pole of the egg, the 

 lead-off to the galvanometer through A C was found to be effective 

 (outgoing current at A), and the lead-off through B C ineffective. The 

 response was outgoing or positive at A after both directions of excita- 

 tion between A B. 



The method of observation is further illustrated by the following- 

 table and plates. Plates 1939-40 taken on the 6th egg (72 hours) 

 are given in detail to show how the magnitude of response varies with 



1939-40. Chick Embryo. 72 hours. 



Arithmetic Increase of Quantity and of Energy by increasing Capacity 

 at Constant Voltage. 



Capacity. 



Pressure. 



Quantity. 



Energy. 



Kesponse. 



lmf. 



8 -4 volts. 



8 '4 mc. 







360 ergs. 



-0010 volt. 



w ) j 



8-4 „ 



16-8 „ 



720 „ 



0-0018 „ 



3 „ 



8-4 „ 



25'2 „ 



1080 „ 



-0022 „ 



4 „ 



8-4 „ 



33-6 „ 



1440 „ 



-0025 „ 



5 » 



8 -4 „ 



42-0 „ 



1800 „ 



0*0027 „ 



* Roy. Soc. Proe..' vol. 68, p. 488 ; vol. 69, p. 181. 



