. Eight lectures on the signs of life from their electrical aspect . One more point to conclude this matter of the surviving human skin. If a piece of Hving 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, i
. Eight lectures on the signs of life from their electrical aspect . One more point to conclude this matter of the surviving human skin. If a piece of Hving 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 case, that of the human skin, the congelation blaze-current is of outgoing direction. 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 o 5 10 m ins. Fig. 51 (4209).—Skin of man. 2nd day after excision. Skin gradually cooled by surrounding the skin-chamber with a freezing mixture. Sudden electromotive discharge (outgo'ng current) at a tempera- ture of - 6° inside the skin-chamber. Be- fore freezing the + responses to + and - single induct
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