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 

 0.3 second, i.e., 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 



FlG. 4o. Cat. Response of skin to , u i 



tetanisation of the sciatic nerve, repeated at muscle Or nerve, but only 



I minute intervals, and lasting for about 5 j n the skin. The question, 



seconds. The deflections at the beginning and u TT , , ,, r 



at the end of the record are standardising^ de- How long does a Cat S foot 



flections by T ^th volt. 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 



5 mins. 



