. Electro-physiology . FIG. 194.—Frog's nerve-muscle preparation. A weak ascending or descending current only dis- charges a closure twitch (b) with any position of electrodes. After 5 min. bath of 1 % KNOg, the excitability of the nerve is lowered. The same current now discharges opening twitches nf equal height with the closure twitches (c, d) from all points of the altered tractjof nerve. After washing with physiological saline (15 min.) the opening twitch disappears again (g, h). saline, the same strength of current will produce uniform break twitches at all points of that part of the nerv
. Electro-physiology . FIG. 194.—Frog's nerve-muscle preparation. A weak ascending or descending current only dis- charges a closure twitch (b) with any position of electrodes. After 5 min. bath of 1 % KNOg, the excitability of the nerve is lowered. The same current now discharges opening twitches nf equal height with the closure twitches (c, d) from all points of the altered tractjof nerve. After washing with physiological saline (15 min.) the opening twitch disappears again (g, h). saline, the same strength of current will produce uniform break twitches at all points of that part of the nerve. But if in such a preparation the electrodes are laid closely together upon the plexus, there will either be a closure twitch alone, with both directions of current, if the connection with the spinal cord is still intact, or else, from the proximity of the cross-section, there will be closing and opening twitches, with descending direction of current. If the action of the potash saltpetre does not affect the immediate proximity of the muscle, but is arrested at about 2 cm. off it, it may be demonstrated that by gradually shifting the electrodes at uniform distance (1 cm.) from the centre to the periphery, the break twitch becomes less and less as the normal portion of the nerve is approached, and an increasing part of it included under the anode—and finally disappears altogether—
Size: 2405px × 2078px
Photo credit: © The Bookworm Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1800, bookdecade1890, bookpublisherlondonmacmillan
