1902.] "Blaze-currents" of the Incubated Hens Egg. 



1 85 



Egg No. 3, also at the end of 48 hours, gave large effects in both 

 directions, larger and more persistent in the upward than in the 

 downward direction. The difference between the reactions of 

 these two eggs was in obvious correlation with their unequal 

 degree of development, for whereas in No. 2 an area vasculosa 

 was only just apparent at one border, in No. 3 it was well 

 formed, and the heart was observed pulsating for more than 12 

 hours after exposure of the blastoderm. 



No. 4 (72 hours) reacted well in both directions, and was normal. 



No. 5 (72 hours) gave me pause. In spite of repeated trial I could 

 not obtain a trace of the reaction that I expected to obtain. 

 Every stimulus of whatever strength and direction gave rise to 

 a slight counter-effect. But the explanation of the result was 

 forthcoming when the egg was opened. No development 

 whatever had taken place. 



No. 6 (72 hours) gave normal reaction in both directions. Develop- 

 ment was normal. 



No. 7 (96 hours), normal reactions and normal development. Re- 

 action abolished by rise of temperature with embryo exposed. » 



No. 8 (108 hours), normal reactions and normal development. Re- 

 action abolished by rise of temperature. 



No. 9 (144 hours), normal reactions and normal development. 

 Reaction abolished by injection of a 2*7 per 100 solution of 

 mercuric bichloride. 



No. 10 (12th day of incubation) gave no blaze in either direction, 

 only polarisation. The contents of the egg were rotten. 



The above series of results was evidently in accordance with the 

 fundamental fact. There was no exception to rule in any of the ten 

 trials. 



Certain of these ten observations were taken in closer detail in order- 

 to get at information as to relation between stimulus and response, 

 effect of strong electrical stimulation, &c, and although these matters 

 will demand considerable further investigation, some of the results 

 may be described now. 



This first series, by no means satisfactory from a chicken-farmer's 

 point of view, was practically conclusive for my purpose, which was to 

 learn whether the presence or absence of a living embryo could be 

 diagnosed from the presence or absence of blaze-currents. 



Other trials made at times of year still more unfavourable as regards 

 probability of development, viz., in August and in November, gave 

 results that were equally satisfactory from my point of view. 



Thus in the second series, No. 1 after 32 hours' incubation gave 

 small blaze effects of ± 0-0010 volt in both directions; the blastoderm 

 was the size of a sixpence, and there was no sign of circulation. Nos. 2 



P 2 



