RECENT ADVANCES IN THERMORECEPTOR 
PHYSIOLOGfY 
H. Hensel 
Physiologlsches Institut 
der Universitat Marburg/Lahn 
Germany 
I am going to discuss some recent problems of thermoreceptors 
which give the organism information about the temperature con- 
ditions of the surroundings. The previous concept of the electro- 
physiology of thermoreceptors was based merely on investigations 
of the afferent impulses in the cat's tongue. Figure 1 shows a 
record from a fine preparation ofthe lingual nerve of the cat during 
mechanical and thermal stimulation of the tongue. Mechanical 
stimulation alone will elicit a large discharge of impulses. During 
cooling we see a smaller single fiber discharge with a partial 
adaptation. When cooling the tongue and touching it at the same 
time, we get both types of discharges. Thus it is quite easy to 
discriminate in the cat's tongue between specific cold receptors 
which respond only to cooling and specific mechano- receptors 
which are not excited by cooling. 
Unfortiinately, we did not stop the experiment at this time, but 
started in Marburg two years ago with investigations of the afferent 
discharges from the cat's external skin. In connection with the 
problems of thermoregulation, it is important to record not only 
from the tongue, which is a rather specialized organ, but also to 
get information about the impulse traffic in the cutaneous nerves. 
We were very surprised to find practically no specific cold fibers 
in the external skin. 
There is quite a number of A fibers showing very much the same 
behavior on cooling and warming as found in the lingual nerve, but 
the cold sensitive receptors in the cat's skin were also sensitive to 
mechanical stimulation, as shown in Figure 2. The discharge of 
this fiber during cooling and warming the skin is the same as has 
been found for the specific cold fibers in the tongue, but on touching 
the skin with a hair, a marked response can be seen. Neither could 
we record any A fiber potentials during warming the external skin 
of the cat. ^y 
