THE SKIN AS AN ORGAN OF SENSE. 555 
sitive to warm and to cold bodies respectively, but not to both; 
and these do not correspond with the pressure-spots, nor to 
those that give rise when touched to the sensation of pain. 
These spots are not placed symmetrically on both sides of the 
same individual, nor on corresponding parts of different indi- 
viduals. So much has been ascertained by experiment. It is 
believed by some of the investigators that these areas are con- 
nected with the nerve-centers by nerve-fibers devoted to con- 
ducting impulses corresponding to the sensations which have 
the beginning of their formation in the different kinds of spots. 
The latter, however, has not been demonstrated. 
While there can be no doubt that these investigations have 
furnished additional facts of great importance, they can not be 
considered as making the whole subject of sensation by the 
skin perfectly clear. For example, how are we to explain why 
a cold body feels heavier than a warm one, as may easily be 
demonstrated to one’s own satisfaction by placing a large coin 
cooled down to near the freezing-point on the forehead beside 
a warmer one? We think such facts are calculated to enforce 
the lesson which we have been endeavoring to impress, viz., 
that our sensations are never single (thermal, tactile, etc.), but 
are compound, one or the other element preponderating ; and 
that all interpretations of sense must take into account this 
fact—and the very important one—that every sensory impres- 
sion is interpreted in the light of our past experience, as well 
as that of the immediate present. 
It has been shown, also, that the extent of the area of skin 
stimulated determines to a large degree the quality of the re- 
sulting sensation. Thus, the temperature of a fluid does not 
seem the same to a finger and the entire hand. This fact is not 
irreconcilable with the existence of the various kinds of ther- 
-mal spots, referred to above, but it does re-enforce the view we 
are urging of the complexity of those sensations which seem to 
us to form simple wholes—as, indeed, they do—just as a 
piece of cloth may be made up of an unlimited number of 
different kinds of threads. 
TACTILE SENSIBILITY. 
As a matter of fact, one may learn, by using a pair of com- 
passes, that the different parts of the surface of our bodies are 
not equally sensitive in the discrimination between the contact 
of bodies—i.e., the judgment formed as to whether at a given 
