. Elements of human physiology. Physiology. SPECIAL SENSES 527 not evenly distributed over the whole surface, but that the special tactile nerve-endings occur at definite spots, between which a strictly localised stimulus (as by the point of a hair) evokes no tactile sensation. These spots can also be mapped out by means of localised electrical stimulation, and it has been found that, using discontinuous stimuli, the sensation produced is also discontinuous so long as the rate of interrup- tion of the current does not exceed 130 per second. The tactile spots are especially marked round each ha
. Elements of human physiology. Physiology. SPECIAL SENSES 527 not evenly distributed over the whole surface, but that the special tactile nerve-endings occur at definite spots, between which a strictly localised stimulus (as by the point of a hair) evokes no tactile sensation. These spots can also be mapped out by means of localised electrical stimulation, and it has been found that, using discontinuous stimuli, the sensation produced is also discontinuous so long as the rate of interrup- tion of the current does not exceed 130 per second. The tactile spots are especially marked round each hair follicle, but a few spots also occur between the hair follicles,. Tactile corpuscle from a papilla of the skin (Kanviei). n, two nerve- fibres passing to the corpuscle ; a, a, varicose ramifications of the axis-cylinders within the corpuscle. and of course are thickly distributed over the palmar side of the hand and fingers. Every tactile sensation has what is termed its local sign, we are able to localise the exact point at which the stimulus is applied to the skin. This power of localisation is intimately connected with the sense of movement and may be impaired by lesions affecting apparently only the efferent side of motor reactions. Intimately connected with the localisa- tion is the power of discrimination of stimuli as single or multiple. Thus if two points tipped with cork, a quarter of an inch apart, be applied to the tongue, they are perceived as two points ; applied to the skin of the back they give rise. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Starling, Ernest Henry, 1866-1927. Chicago : W. T. Keener
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