Eight lectures on the signs Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 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
Eight lectures on the signs Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 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 + ar>d + 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,
Size: 1288px × 1553px
Photo credit: © Bookworm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: archive, book, drawing, historical, history, illustration, image, page, picture, print, reference, vintage
