3. The organ of sense—the ear.
4. The nerves—cells and fibres involved in receiving and conveying the sense stimulus.
5. The interpreting cells.
6. The reacting mind, which interprets the impression as an image of sound.
The different factors are somewhat arbitrarily illustrated in the accompanying diagram, the arrows indicating the physical stimulation and the conscious response:
Of the six factors involved in the sensation, 1 and 2 are purely physical and belong to the science of acoustics; 3, 4, and 5 are physiological; 6 is conscious, or psychological. It is because they always involve the immediate presence of some physical object, that the sensation elements involved in ordinary perception are spoken of as immediate, or presentative, elements of knowledge.
CLASSIFICATION OF SENSATIONS
Our various sensations are usually divided into three classes as follows: