THERMORECEPTOR PHYSIOLOGY 
subjects. We are greatly indebted to our medical students for their 
cooperation as subjects in these experiments. 
MOVIE: CUTANEOUS AFFERENT NERVES IN 
HUMAN SUBJECTS 
We use the superficial branch of the radial nerve which can be 
found easily by palpation. The course of the nerve is marked on the 
skin. Exposure of the nerve is made under a very short general 
anaesthesia lasting for about five minutes. The experiment proper 
is performed in the non-anesthetized subject. If the preparation is 
made carefully, the subject will feel quite comfortable. 
The nerve preparation is made under a stereo-microscope. The 
superficial branch of the radial nerve is quite a thick nerve, about 
four or five millimeters in diameter, but we use only a very small 
part of the nerve, about one tenth. The nerve consists of several bun- 
dles connected with loose connective tissue. Before separating a 
bundle, the intact nerve is tested by means of weak electrical shocks 
in order to find the part with the most suitable receptive field. Then 
this bundle, which is about 0.5 mm in diameter, is separated from 
the remaining part of the nerve and cut proxim ally. At this moment, 
the subject feels a burning sensation in the receptive field which dis- 
appears after a few seconds. 
The electrode is fixed in a micromanipulator and adjusted to the 
nerve strand. The nerve is put onablack plate for the final dissec- 
tion into thin filaments. These filaments, of course, do not always 
contain single fibers in an anatomical sense, but they are thin 
enough to get mostly a single fiber discharge. The afferent impulses 
are recorded by a cathode ray oscillograph, whereas galvanometers 
are used for recording the skin temperatures. Heating and cooling 
the skin is brought about by water-circulated thermodes which rest 
on the skin in the same position for the whole time. Four thermostats 
set at various temperatures are connected alternatively with the 
thermode by means of a switch. 
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