made upon a freshly killed animal, affords a very convenient means of class-demonstration of the fundamental fact. The response is elicited by stimulation of the sciatic nerve after the latter has ceased to pro- voke muscular contraction, and can then be most conveniently demon- strated (and recorded) without resort to the curarisation and artificial respiration necessary in the case of the living animal. The method and its results will be made sufficiently apparent by the following experiments and figures :
Experiment 1 . Electrical Response of the Skin to Indirect Excitation through the Sciatic Nerve.
Cat decapitated -Both sciatics exposed and cut Large pad of each hind foot led off to galvanometer by unpolarisable electrodes Tetanic excitation of peripheral end of one or other sciatic for 5 seconds at intervals of 5 minutes Berne coil at 1000 units supplied by two Leclanches.
Deflection + signifies that the skin of the right side is electro- positive, i.e., that it is traversed by an ingoing current (directed from left side to right through the galvanometer).
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Remarks.
Muscles contract.
Do.
Do.
Do. faintly. No contraction.
Do.
Do.
Do.
Do.
The effect of excitation was thus in each instance an ingoing current of the skin of the excited side.
Experiment 2. Similar Experiment. Excitation of Right Sciatic at
Time after
Deflection by
excitation of
Deflection by
excitation of
decapitation.
left sciatic.
right sciatic.
Mins.
Volt.
15
-o-oioo
20
-0-0150
25
-0-0110
-
30
+ 0-0050
35 and 36
-o-oioo
+ 0-0160
40 and 41
-0-0060
+ 0-0100
45 and 46
-o-ooio
+ 0-0060
50 and 51
Nil
+ 0-0010
55 and 56
Nil
Nil
Time, mins.
20
30
40
50
60
70
Intervals of 10 minutes. Deflection. Remarks.
+ 0-0050 + 0-0045 + 0-0035 + 0-0020 + 0-0005 Nil
Faint contraction. No contraction.
Do.
Do.
Do.
