6. The problem may arise of the reliability of impressions of habitual pressure. Weber made the earliest experiments, later verified by Fechner, showing that the sensation of weight differs a great deal on different portions of the skin. The most sensitive are the forehead, the temples, the eyelids, the inside of the forearm. The most insensitive are the lips, the trunk and the finger-nails. If piles of six silver dollars are laid on various parts of the body, and then removed, one at a time, the differences are variously felt. In order to notice a removal the following number must be taken away:
Five dollars from the middle of the back,
Further examinations have revealed nothing new. Successful experiments to determine differences between men and women, educated and uneducated, in the acuteness of the sense of pressure, have not been made. The facts they involve may be of use in cases of assault, choking, etc.
What lawyers have to consider in the transition from purely sensory impressions to intellectual conceptions of these impressions, is the possibility of later reproducing any observed object or event. Many so-called scientific distinctions have, under the impulse of scientific psychology, lost their status. Modern psychology does not see sharply-drawn boundaries between perception and memory, and suggests that the proper solution of the problem of perception is the solution of the problem of knowledge.[189]
With regard to the relation of consciousness to perception we will make the distinctions made by Fischer.[190] There are two spheres or regions of consciousness: the region of sensation, and of external perception. The former involves the inner structure of the organism, the latter passes from the organism into the objective world. Consciousness has a sphere of action in which it deals with the external world by means of the motor nerves and muscles, and a sphere of perception which is the business of the senses.
External perception involves three principal functions: apprehension, differentiation, and combination. Perception in the narrower sense of the term is the simple sensory conscious apprehension of some present object stimulating our eyes. We discover by means of it what the object is, its relation to ourselves and other things, its distance from us, its name, etc.