BBA ANIMAL PHYSIOLOGY. 
PRESSURE SENSATIONS. 
1. There is a relation between the intensity of the stimulus 
and the sensation resulting, and this limit is narrow. The 
greater the stimulus the more pronounced the sensation, though 
ordinary sensibility soon passes into pain. Weber’s law (to be 
explained later) holds in the case of the skin as for other senses, 
2. The duration of the sensation is very brief. It is said that a 
card in which holes have been punched, so that when in rota- 
tion it may bear on the skin, may be made to touch one of its 
holes against the finger as often as fifteen hundred times ina 
second before the sensations are fused. 3. The law of contrast 
may be illustrated by passing the finger up and down in a ves- 
sel containing mercury, when the pressure will be felt most dis- 
tinctly at the point of contact of the fluid. 4. Pressure is much 
better estimated by some parts than others; hence the use of the 
tips of the fingers in counting the pulse, palpating tumors, etc. 
THERMAL SENSATIONS, 
1. The law of contrast is well illustrated by this sense; in 
fact, the temperature of a body exactly the same as that of the 
part of the skin applied to it can scarcely be estimated at all. 
The first plunge into a cold bath gives the impression that the 
water is much colder than it seems in a few seconds after, when 
the temperature has in reality changed but little; or, perhaps, 
the subject may be better illustrated by dipping one hand into 
warmer and the other into colder water than that to be ad- 
judged. The sample feels colder than it really is to the hand 
that has been in the warm water, and warmer than it is to the 
other. 2. The limit within which we can discriminate is at most 
small, and the nicest determinations are made within about 27° 
and 33° C.—i.e., not far from the normal temperature of the 
body. 38. Variations for the different parts of the skin are 
easily ascertained, though they do not always correspond to 
those most sensitive to changes in pressure. The cheeks, lips, 
and eyelids are very sensitive to pressure, 
Recent investigations have revealed the fact that there 
are in the skin “pressure-spots,” and “cold-spots” and “ heat- 
spots”—i.e., the skin may be mapped out into very minute 
areas which give when touched a sensation of pressure differ- 
ent from that produced by the same stimulus in the intermedi- 
ata raoinnas and in lilzta mannar ara thara araaa whieh are sens 
