Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 28 THE SIGNS OF LIFE [LECT. zero current, , whether the accidental current upon which it is superposed be positive or negative. Or to use a familiar laboratory mnemonic—the normal excited eyeball always ' looks through its own galvanometer.' (See Fig. 3). There is always a considerable interval of time between the incidence of light and the electrical response; sometimes the delay at ' make ' of light may be so great as to be measurable by a stop-watch, but in such cases the delay at ' brea
Eight lectures on the signs of life from their electrical aspect eightlecturesons00wall Year: 1903 28 THE SIGNS OF LIFE [LECT. zero current, , whether the accidental current upon which it is superposed be positive or negative. Or to use a familiar laboratory mnemonic—the normal excited eyeball always ' looks through its own galvanometer.' (See Fig. 3). There is always a considerable interval of time between the incidence of light and the electrical response; sometimes the delay at ' make ' of light may be so great as to be measurable by a stop-watch, but in such cases the delay at ' break ' is much less considerable, and I have considered the interval at make as a period of hesitation (vide infra) rather than as a true physiological lost-time. But even under the most favourable conditions, with fresh and typically reacting eyeballs, I have FlG. 12.—Frog's eyeball. Electrometric record of the normal response at beginning (a) and end (u>) of illumination. The retinal delay is in each case about £ sec., , approximately the same as that of cortical grey matter. never seen the latency as short as given by Dewar and MacKendrick, and more recently by Fuchs—viz., ' less than T^th of a second.' The shortest intervals I have measured have been of about i second, no difference being detectable between the make and the break deflections in this respect. These values have been obtained from galvanometer records, of which Fig. 11 is an example, and are subject to a correction, by
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