IOWA ACADEMY OF SCIENCE 
333 
Our findings on these points, briefly summarized from a number of 
stimulations on the forearm (both right and left arms, and the front or 
back of the arm being employed in the experiments) were as follows : 
Stimulation by a dull pencil point or a round, blunt-pointed peg 
brought out separate wheals for each point touched, and these wheals 
appeared within three minutes after the stimulus. They reached their 
maximum vividness between five and ten minutes after the stimulation. 
These wheals measured from 3mm. to 5mm. in diameter varying in size 
with the fineness of the point used in stimulation. For example, a fine 
point gently pressing the skin brought out a beadlike disc, while pres- 
sure from the flat end of a lead pencil produced a blotch with the same 
general characteristics as the wheals. 
A number of later experiments confirmed our findings as to the in- 
terval between stimulation and the appearance of the figures on the arm. 
The wheals remained visible from half an hour to an hour and a half, 
gradually sinking back into the normal smoothness and color of the sur- 
rounding skin. Frequently a red blotch or line would be the last visible 
trace of the wheals. The size of the individual wheals varied with the 
character of the instrument used, and the form was still further modified 
when the corner of a card was drawn across the skin. In such a test 
the reaction took the form of a welt or ridge resembling fine beading 
and having a conspicuous elevation perceptible to the touch, as the fin- 
gers were drawn across it. The wheals and the ridges thus produced at 
the will of the experimenter involved merely the contact to insure their 
appearance day after day, and with equal clearness whether the experi- 
ment were tried early in the morning or late in the afternoon. Miss M. ’s 
ability to duplicate the results in subsequent tests showed that the reac- 
tions were not due to any temporary physiological condition. This fact 
was further confirmed by Miss M. ’s own testimony of having long been 
familiar with this quality of sensitiveness to tactual impressions. 
Different parts of the body were not equally sensitive to the same 
degree of stimulation. There was very little difference between the dis- 
tinctness of the wheals on the front and on the back of the arm. Any 
slight advantage might easily have been attributed to inequality of stim- 
ulus or to the difficulty of bringing the two surfaces into comparison at 
the same time. However, when a test was made on the tip of the index 
finger, with its decided advantage of tactual sensitiveness, no wheal or 
welt appeared. Repeated experiments on those parts where the epider- 
mis is tough or calloused failed to bring the results described above. 
Miss M. \s own report of tests performed under the same: general condi- 
tions but on different parts of the body shows that the condition of 
