1896-97.] 
Chairman’s Opening Address. 
191 
now termed “hot spots,” and near these other spots called “cold 
spots.” A copper point, of the temperature of the skin, applied to 
a cold spot, excites a sensation not of heat, but of cold, and, on 
the other hand, the same rod applied to a hot spot excites a sensa- 
tion of heat. So we have pressure spots, hot spots, and cold spots. 
These spots are not indiscriminately mixed, hut there are little 
adjoining areas in which one of the three kinds predominates. 
Temperature spots are insensitive to pain, that is to say, a fine 
needle may be pushed into such a spot without causing pain. 
Further, as was shown by Stanley Hall and Donaldson, in 1885,* 
when a metallic point conveying a current of electricity was carried 
along the surface of the skin there was considerable diversity of 
sensation at different points, so that the authors observed cutting- 
pain points, thrill points, tickle points, points at which the sense of 
motion of the irritating body appeared to be increased, and blind or 
dead points, to which no sensation was referred. This is the only 
observation I have met with bearing on the effects on sensations 
produced by weak electrical stimulation of the skin. It would 
appear, therefore, that a dermal sign (that is, the effect in con- 
sciousness of irritation in one way or another of an area of skin) 
is often a mixture of feeling, and that this mixture may give a 
characteristic feature to each local area of skin. 
It is difficult to conjecture what skin elements are affected by 
the rapid induction currents under consideration. They do not 
produce pressure in the ordinary sense ; so far as I can make out, 
they do not produce sensations of temperature ; and the sensations 
are not of a painful character. They may act simply on the 
delicate sensory nerve filaments everywhere abounding, and they 
give rise to sensations of a peculiar kind, a sense corresponding to 
electrical stimulation and to nothing else. 
So far as I am aware, no observations have been made on the 
stimulation of sensory skin nerves except with reference to the 
production of reflex acts. The effects of stimuli, varying in 
number, in intensity, in rhythm on consciousness, have not been 
studied. It is well known that a single stimulus applied to a 
motor nerve will cause a single twitch, and the characters of a 
* G. S. Stanley Hall and H. H. Donaldson, “Motor sensations in skin,” 
Mincl , October 1885. 
