Elements of psychology / by George Croom Robertson ; edited from notes of lectures delivered at the college, 1870-1892, by C.A. Foley Rhys Davids.

Robertson, George Croom, 1842-1892.

Date:: 1896

Credit: Elements of psychology / by George Croom Robertson ; edited from notes of lectures delivered at the college, 1870-1892, by C.A. Foley Rhys Davids. Source: Wellcome Collection.

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$retaining a sense of touch, lose the capacity of feeling pain through pricks. On the other hand, touch and temperature pass by insensible degrees into pain, when the excitation has reached a certain pitch, so that pain seems due to degree or mode of excitation of the same nerve-fibres. Again, we have not the same proof that there are different fibres for pain and touch, as we have that there are different fibres for temperature and touch. In these there is every reason to believe that each kind of sensation is connected with different nerve-i?«(/z'«^j and different fibres of the same nerve. At parts of the skin we have touch and temperature, at others temperature and not touch. Investigations even seem to show that on a minute scale there are heat-spots and cold-spots on the skin, where we feel only heat and only cold respectively h Hence skin sensibility is a complex, a nest, or matrix of sensation.s, nor perhaps has research yet exhausted its specialisations. And each mode of it is both general and special. How far special.? In so far as contact, shifted the fraction of a millimetre on the skin, may indicate a change in feeling from heat to cold or to sense of touch only. The sensations of touch proper are highly discriminable, of considerable qualitative variety, indefinitely numerous. As to the physiological conditions, the nerve-endings of touch vary greatly at different parts of the body, the full import whereof will be evident later. They are, to take extremes, very different at the tips of the fingers and tongue from those in the interscapular region of the skin. That such differences exist and are parallel with subjective differences is characteristic of special sense. Touch, therefore, and temperature, though nearly related to general sensibility, are essentially special as well, and constitute, as we have said, a bridge between the two. * Cf. Donaldson, ‘On the Temperature Sense,’ Mind, ]vi\y, 1885.$