18 SPECIAL SENSES. 



exquisitely sensitive. The appreciation of temperature also 

 varies in different parts, this probably depending to a great ex- 

 tent upon habitual exposure. Some parts, as the soles of the 

 feet or the axilla, are peculiarly sensitive to titillation. The 

 sense of touch, however, by which we appreciate the size, 

 form, character of the surface, consistence, etc., of objects, is 

 developed to a greater degree in some parts than in others; a 

 fact which can be very readily explained, in some instances, 

 by the anatomical arrangements of the peripheral sensory 

 nerves. When we wish to ascertain those properties of ob- 

 jects revealed by the sense of touch, we generally employ 

 the fingers. This sense is capable of education, and is al- 

 most always extraordinarily developed in persons who are 

 deprived of other special senses, as sight or hearing. The 

 blind learn to recognize individuals by feeling of the face. 

 A remarkable instance of this is quoted in works on physi- 

 ology, of the blind sculptor, Giovanni Gonelli, who was said 

 to model the most striking likenesses entirely by the sense of 

 touch. Other instances of this kind are on record. The 

 blind have been known to become proficients in conchology 

 and botany, guided simply by the sense of touch. It is re- 

 lated of a blind botanist, that he was able to distinguish or- 

 dinary plants by the fingers and by the tip of the tongue. It 

 is well known that the blind learn to read with perfect facility, 

 by passing the fingers over raised letters but little larger 

 than the letters in an ordinary folio Bible. 1 Rudolphi cites 

 the remarkable faculty acquired by Baczko, of distinguishing 

 the colors of fabrics by the sense of touch alone. 3 



An exceedingly ingenious and accurate method of deter- 

 mining the relative delicacy of the tactile sensibility of dif- 

 ferent portions of the cutaneous surface was devised a num- 

 ber of years ago (1829) by E. H. Weber, whose researches on 

 this subject, which have been repeatedly confirmed by other 



1 CARPENTER, Cyclopaedia of Anatomy and Physiology, London, 1849-1852, 

 vol. iv., part ii., p. 1179, et seq., Article, Touch. 



8 RUDOLPHI, Grundiss der Physiologic, Berlin, 1823, Bd. ii., S. 85. 



