If after exact compensation of this normal current a single induction
shock is sent through the pad, either in the ingoing or in the outgoing
direction, the effect or, properly speaking, the after-effect is in nearly
every instance outgoing, as in the case of the frog's skin. The
few instances in which I have witnessed an ingoing response have
been in the case of fresh skin, taken soon after decapitation, and
tested by comparatively weak induction shocks. (I find in my
laboratory notes only one instance of a late ingoing response 3 days
after decapitation.) In such cases the ingoing response has been of
comparatively low voltage, and has given place to an outgoing re-
sponse at the end of a few hours. From review of a considerable
number of observations I conclude that outgoing response is the rule,
ingoing response the exception. I have kept the former under
systematic observation up to 60 hours post-mortem, but have found
under the conditions of observation that it may disappear at an earlier
period from the skin of ill-nourished animals.
The physiological action of the skin is indicated : 1, by its invariable direction with both directions of excitation ; 2, by its complete aboli- tion after immersion of the skin in hot water.
A series of responses provoked at short intervals exhibits summa- tion. Tetanisation by alternating induction shocks in both pairs of directions, excites a larger response than that aroused by a single induction shock.
These several points will be made sufficiently clear by the following experiments and figures :
Experiment 4. Direct Excitation. Same Cat as that of Experiment 2.
Large pad cut off and set up between unpolar electrodes 9 hours after
decapitation. Compensation. Direct Excitation in + (outgoing) and
- (ingoing) directions. Berne Coil. 8 Leclanche's in primary circuit.
10,000 units.
| A table should appear at this position in the text. See Help:Table for formatting instructions. |
Time.
Excitation.
Response.
After immersion in
hot water.
9 hours
Tetan.{7}
+ -0056 volt.
T> J" m -+l
Do. < , > \br.- j
+ '0100
24 hours
Single break +
+ 0-0025
trace.
+ -0032
+ trace.
- {;}
+ 0-0175
+ -0004
{.1}
+ 0-0242
- 0-0004
