1154 
Physiology. — “On the value of the simultaneous registration of 
the plethysmogram and the psychogalvanic reaction. By Prof. 
E. D. Wiersma. 
(Communicated in the meeting of December 18, 1915), 
The respiration causes distinct fluctuations in the length and height 
of the pulse, in the blood-supply of the hand and in the position 
of the diacrotism. These fluctuations disappear under all influences 
which impel the heart to more labour, that is to say they disappear 
owing to bodily influences, but also in consequence of psychical 
agents such as emotions. 
These emotions likewise bring about important modifications in 
the so-called cutaneous currents. If a zine plate is taken in one 
hand, which is connected by a conducting-wire with a stick of 
carbon held in the other, an inserted galvanometer will deflect. 
This electric current which is pretty stable at a quiet attitude of 
the subject is called the ‘‘rest-current”. This investigation was first 
carried out by Ffré in 1888, and subsequently repeated by Tar- 
CHANOFF in 1890. I shall pass by the many researches made after- 
wards. An important question was where the potential differences 
arise. They may originate in the body, and then we speak of 
endosomatie electromotive force. If they arise ontside the body by 
the action of perspiration on the zine, the electromotive force is 
exosomatic. 
Where the potential difference takes its origin, may be determined 
in the following manner. If it takes place outside the body, an 
exchange of the hands will not affect the galvanometric deflection. 
Only by changing the conducting wires we can reverse the current. 
If the potential difference is found in the skin, the galvanometer 
will deflect as much in the opposite direction’). It appears that in 
the method I denoted above, the exosomatie electromotive force 
preponderates to such an extent that in these experiments it is the 
only factor we need take into account. 
The above-mentioned rest-current is considerably strengthened by 
every sensory stimulus and by every psychical labour. Now it is 
of importance to determine what causes this increase. When namely 
a current in the opposite direction is made to counterbalance all 
electromotive forces, so that the galvanometer points to zero, not a 
single stimulus will produce a deflection of the galvanometer. It 
follows that such a stimulus produces no electromotive force, but 
1) A. Grecor and S. Löwe. Zeitschrift für die Ges. Neurol. u. Psychiatrie p. 411. 
