as normal as possible in all respects.

A great many laboratories have now been established in connection with
the universities in Germany, France, and the United States. They
differ very much from one another, but their common purpose is so to
experiment upon the mind, through changes in the stimulations to which
the individual is subjected, that tests may be made of his sensations,
his ability to remember, the exactness and kind of movements, etc.

The working of these laboratories and the sort of research carried out
in them may be illustrated best, perhaps, by a description of some of
the results, apparatus, methods, etc., employed in my own laboratory
during the past year. The end in view will, I trust, be considered
sufficient justification for the degree of personal reference which
this occasions; since greater concreteness and reality attach to
definite descriptions such as this. The other laboratories, as those
at Harvard and Columbia Universities, take up similar problems by
similar methods. I shall therefore go on to describe some recent work
in the Princeton laboratory.

Of the problems taken up in the laboratory, certain ones may be
selected for somewhat detailed explanation, since they are from widely
different spheres and illustrate different methods of procedure.

I. _Experiments on the Temperature Sense._--For a score of years it
has been suspected that we have a distinct sense, with a nerve
apparatus of its own, for the feeling of different temperatures on the
skin. Certain investigators found that this was probably true; it is
proved by the fact that certain drugs alter the sensibility of the
skin to hot and cold stimulations.

Another advance was made when it was found that sensations of either
hot or cold may be had from regions which are insensible at the same
time to the other sort of stimulation, cold or hot. Certain minute
points were discovered which report cold when touched with a cold
point, but give no feeling from a hot object; while other points would
respond only with a sensation from heat, never giving cold. It was
concluded that we have two temperature senses, one for hot and the
other for cold.

Taking the problem at this point, Mr. C.[3] wished to define more
closely the relation of the two sorts of sensation to each other, and
thought he could do so by a method by which he might repeat the
stimulation of a series of exact spots, very minute points on the
skin, over and over a