VII.] 



THE CONGELATION BLAZE 



119 



voit 



One more point to conclude this matter of the surviving 

 human skin. If a piece of living skin, placed between electrodes 

 and connected with a galvanometer in the usual way, is 

 gradually cooled in a freezing- 

 box, we shall notice, at a 

 given temperature of about 

 - 5, a sudden deflection of the 

 galvanometric spot indicative 

 of a sudden electromotive 

 change. The effect is due to 

 the sudden congelation of the 

 under-cooled tissue. This 

 " congelation blaze," which is 

 manifested by vegetable as 

 well as by animal tissues, is in 

 general their last sign of life ; 

 if the frozen tissue is thawed, 

 and then cooled a second 

 time, there is little or no 

 second blaze according as the 

 tissue has been more or less 

 completely killed by the first 

 proceeding. In the present 



10 m ins. 



case, that of the human skin, 

 the congelation blaze-current 

 is of outgoing direction. 



FlG. 51 (4209). Skin of man. 2nd 

 day after excision. Skin gradually cooled 

 by surrounding the skin-chamber with a 

 freezing mixture. Sudden electromotive 

 discharge (ouigo : ng current) at a tempera- 

 ture of - 6 inside the skin-chamber. Be- 

 fore freezing the + responses to + and - 

 single induction shocks were +0.004 ar >d 

 + 0.008 volt. After freezing, the + responses 

 were absent, being replaced by small 

 and + polarisation effects. On recongela- 

 tion no second discharge was observed. 



Alterations of electrical resistance occur in marked degree in 

 connection with the electromotive effects that first attract our 

 attention. Surviving skin as it dies exhibits a fall of resistance. 

 There is a well-marked diminution of resistance as the im- 

 mediate consequence of electrical excitation ; Fig. 50 incident- 

 ally shows this. And in the course of cooling, there is first a 

 gradually increasing resistance, then at the point of congelation 

 a sudden increase of resistance, which in some instances is 

 preceded by a small and evanescent diminution, not unlike a 

 congelation blaze, which, however, I have reason to attribute to a 

 slight rise of temperature and of conductivity occurring when 

 the under-cooled tissue juices pass from the liquid to the solid 



