[Footnote 26: Bidwell describes this "black process" or "negative after-image" of a bright, white light as being of a blackness more intense than the ordinary blackness of an entirely dark room. This is perfectly true. The black image, however, lasts for a very much longer time than the recurrent images of the same light. Often this velvety black band would trail along behind the moving light for the distance of a foot or more, gradually lightening into the darkness of the background.] [Footnote 27: The intensities used with white light are all less than an eight-candle-power electric lamp placed at about a foot behind the opening and covered with two pieces of ground glass.] [Footnote 28: McDougall, 1901, 1903.] FEELING THE EXPRESSION OF FEELINGS BY F. M. URBAN The material of this paper was obtained by an experimental investigation which was carried on in the Harvard laboratory from February, 1904, till June, 1905. The immediate purpose of these experiments was a study in the expression of the feeling-tone of simple sense-stimuli. Breathing and circulation were the functions the changes of which were observed by tracing the curves of thoracal and of abdominal breathing and the sphygmographic curves simultaneously. Acoustical, tactual, pain, and smell sensations were studied in this way, special attention being devoted to the smell and pain sensations. These stimuli have the advantage that the physiological reactions of the subject are more uniform than the reactions to other stimuli. The number of experiments performed in this investigation was large, although a subject was never experimented on for more than forty minutes, because the facilities of the laboratory allowed a continuous experimenting for several hours a day on different subjects. All the experiments were performed on trained subjects. Only the changes in the form of the sphygmographic curve will be discussed in this paper. The results of this observation confirm the observations of previous investigators in so far as the same changes in the curves were observed and the introspections of the subject were, on the whole, similar to those obtained by other observers. It does not seem probable, however, that a satisfactory discussion of the results can be given on the basis of merely mechanical measurements of the curves, and it, therefore, seemed necessary to reconsider the principles of the theory of the sphygmographic curves.