Outlines of human physiology / by F. Schenck and August Gürber, authorized translation from the second German edition by Wm. D. Zoethout with a preface of Jacques Loeb.

Friedrich Wilhelm Julius Schenck

Date:: 1900

Credit: Outlines of human physiology / by F. Schenck and August Gürber, authorized translation from the second German edition by Wm. D. Zoethout with a preface of Jacques Loeb. Source: Wellcome Collection.

Provider: This material has been provided by the Augustus C. Long Health Sciences Library at Columbia University and Columbia University Libraries/Information Services, through the Medical Heritage Library. The original may be consulted at the the Augustus C. Long Health Sciences Library at Columbia University and Columbia University.

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$(d) The Vater-Pacini corpuscles, whose capsule is com- posed of man\r concentric lamellae. 2. Qualities of cutaneous sensations.—There are four ■qualities of cutaneous sensations, viz., touch, heat, cold, and pain. These various qualities are located in various parts in the skin. There are portions whose stimulation calls forth tactile sensations only, so-called tactile or touch points; we ■can also discriminate warmth, cold, and pain points. These four kinds of points are not evenly distributed over the whole body. Some of them are lacking in certain regions of the body, e.g. the central part of the cornea has only pain points, while its peripheral portion is provided with pain and cold points. The glans penis contains no tactile points ; a part of the mucous mem- brane of the cheek lacks pain points. In those regions of the body where the four kinds of points are all found, the pain points are generally most numerous, then follow the tactile and cold points, while the warm points are least numerous. (a) Tactile sensation. — The adequate stimulus for the tactile sense organs is the pressure exerted upon the skin. Concerning the nature of the stimulation of nerve endings by pressure nothing is known. Stimulation by pressure occurs only at the boundary of the portion of the skin pressed, where, therefore, a fall in pressure exists. For example, if a finger is dipped in mercury, sensations of pressure are not felt in the portion of the finger below the mercury, but at the circle formed by the level of the mercury. Tactile sensations can also be produced by pulling the skin. If the pull is exerted upon a very small area of the skin, for example upon an individual tactile point, the sensation produced is nearly like that produced by pressure. Only when a larger portion is stimulated can Ave differentiate between pull and pressure. The organs for the tactile sensation are probably the nerve wreaths of the hair [Haarnervenkranze] and the corpuscles of Meissner, for the following reasons : I. In the regions of the body covered with hair, a tactile point is found very near the exit of each hair. The hair serves as a tactile apparatus, forming a lever whose shorter arm is in contact with the sensory mechanism in the skin, while the longer arm receives the stimulus.$