Bauhaus-Universität Weimar

Titel:
Plethysmographic Experiments on the Vaso-Motor Nerves of the Limbs [From the Journal of Physiology, Vol. VII, Nos. 5 & 6, Offprint]
Person:
Bowditch, H. P. J. W. Warren
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit39635/28/
442 
IL P. LOW DI T(JII AND J. W. WARREN. 
Duration of the Stimulation. 
In the experiments thus far described the stimulation was kept up 
long enough to produce the characteristic effect and usually lasted from 
6" to 20". A certain number of experiments were, however, made with 
longer and with shorter periods in order to determine the effect of 
variations in the duration of the stimulation upon the vaso-motor 
phenomena. In general it may be said that the intensity and not the 
character of the phenomenon varies with the duration of the stimulation. 
In other words contractions and dilatations both become more pronounced 
the longer (within certain limits) the stimulation is maintained. The 
question : what are the limits within which this statement is true ? is 
one which the experimental method here employed did not enable us to 
answer with precision, and its investigation is therefore postponed until 
some future occasion, when, with a different form of recording apparatus, 
more accurate results may be looked for. The following table shows the 
result of a few observations all made on the same animal with a weak 
tetanus of the nerve lasting from 1' to 6". 
Table III. 
Tetanic stimulation 1 = 10. 
Duration of stimulation. 
1" 
2" 
4" 
6" 
Number of observations 
2 
5 
2 
4 
Average contraction 
3-7 
6-4 
8-0 
8-3 
Average dilatation 
0 
0-8 
o-o 
1-4? 
It will be noticed that the constriction increases at first rapidly and 
then more slowly with the duration of the stimulation. 
In this connection it may be mentioned that in one experiment a 
tetanic stimulation was applied for fifteen minutes to the sciatic nerve. 
The result was a constriction steadily maintained during the continuance 
of the irritation and a return to the normal state on its cessation. 
The vaso-constrictor fibres seem, therefore, not to be very easily 
fatigued. 
Temperature of the Limb. 
In the above experiments the glass vessel enclosing the leg of the 
animal was at the beginning of the experiment filled with water at the
        

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