1156 
repeatedly to identify organic deafness, and to demonstrate functional 
or organic deafness where it would have been very difficult or 
impossible to arrive at results by other methods. 
After the stimulus the pulse (Fig. Ll) grows regular, its height 
decreases, the dicrotism is lower and the blood-supply of the hand 
diminishes. Sometimes, however, these modifications in the plethys- 
mogram do not occur. In cases of hysteria. for instance, the plethys- 
mogram often does not undergo the slightest change, while the 
psychogalvanic reaction clearly manifests itself. (See Fig. il). 
A ws Respiration 
REEK an) 
OOMEN 0 
Clap hel 
Fig. 3. 
The insensibility to stimuli, of the plethysmogram finds its expla- 
nation in the fact that all changes otherwise effected. by the stimulus 
have already taken place. The heightened emotionality of the hys- 
teria has caused them. The lines of the plethysmogram enable us, 
therefore, to form an opinion on the existence of more permanent 
mental states. Wherever there is preoccupation, with normal persons 
as well as in pathological conditions, the respiration oscillations of 
the plethysmogram have diminished or disappeared. The above 
curve originates from a patient who had suddenly become deaf. 
This investigation, at which the stimulus consisted in the ticking of 
an electric bell, proves distinctly that organic deafness was out of 
the question. The patient showed, moreover, a number of hysteric 
stigmata. After a treatment of some weeks the deafness had entirely 
disappeared. An organic deafness, which is sometimes very difficult 
to identify, can easily be discovered by this method. 
The absence of the respiratory oscillations in the plethysmogram 
is pretty regularly to be seen in the curves of melancholic or cata- 
tonie stupor-patients. This suggests, therefore, that. here we have not 
