. Eight lectures on the signs of life from their electrical aspect. Electrophysiology. 106 THE SIGNS OF LIFE [lect. that the phenomenon is comparatively slow and prolonged, so that it can be followed and observed by galvanometer almost as well as by electrometer ; the former instrument has indeed inertia and " lost time," but these are not considerable in com- parison with the physiological inertia and lost time of the change observed ; this particular galvanometer has a lost time of about second, z>., only one-tenth that of the physiological lost time under observation; the e
. Eight lectures on the signs of life from their electrical aspect. Electrophysiology. 106 THE SIGNS OF LIFE [lect. that the phenomenon is comparatively slow and prolonged, so that it can be followed and observed by galvanometer almost as well as by electrometer ; the former instrument has indeed inertia and " lost time," but these are not considerable in com- parison with the physiological inertia and lost time of the change observed ; this particular galvanometer has a lost time of about second, z>., only one-tenth that of the physiological lost time under observation; the electrometer has no appreciable lost time, which of course, is an advantage. The voltage of the response is greater in the galvano- metric than in the electrometric curve, but that is only incidental to the fact that in the former case the response was taken to tetanisation, and in the latter to a single induction shock; perhaps also the nerve-skin was becoming fatigued. Such fatigue, in consequence of repeated action, does in fact always appear in more or less pronounced degree. Here is an instance in which it is very well marked. The direct (blaze) effects that persist for hours or days after the indirect ex- citability of the skin and the indirect and direct ex- citability of muscle have dis- appeared. I am here refer- ring to the direct and indirect excitability of muscle in the usual acceptation of these terms; I have not yet studied in detail the direct (blaze) effects in either muscle or nerve, but only in the skin. The question, " How long does a cat's foot live ?" is, I believe, to be answered by reference to the blaze-currents of the skin, which I have found in a favourable case as long as a week post- mortem, when no other sign of life on any other tissue could be detected. And by a favourable case I mean that of a. o 5 mins. Fig. 45.—Cat. Response of skin to tetanisation of the sciatic nerve, repeated at I minute intervals, and lasting for about 5 seconds
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