4 Proceedings of the Royal Physical Society. 



patterns themselves present infinite variety as regards design. 

 It seems to me that the sense of touch cannot require papillae 

 arranged in special patterns upon special areas constant alike 

 in hand and foot, and that therefore some other explanation 

 of the presence and importance of papillary ridges is not only 

 possible but is obligatory. 



If we examine the raised areas upon which papillary 

 ridges assume the form of patterns, we shall find that they 

 occur on the palmar or plantar aspects of the terminal 

 phalanges of the digits ; on the ball of the thumb and ball of 

 the little finger, and on positions which correspond thereto 

 in the sole of the foot ; on three small elevations which are 

 situated close to the clefts between the four fingers and four 

 outer toes. It must be evident to every zoologist that the 

 elevations just enumerated correspond to the '' pads " in the 

 feet of five-toed mammals. Therefore I hold that these 

 " pattern-areas " are merely modified " pads,'' whose shape 

 and prominence have become reduced, and that the par- 

 ticular " patterns " are merely accidental concomitants of the 

 arrangement of rows of papillae upon a surface which was 

 originally a projecting point capable of enlarging during 

 growth into the form of a modified hemispherical dome. 

 The occurrence of papillae arranged in rows forming ridges, 

 whether in the transverse direction or disposed so as to form 

 patterns, requires further explanation. To fully appreciate 

 the value and importance of this arrangement, it is necessary 

 to keep in mind the constancy with which the mouths of 

 the sweat-ducts open upon the summits of the ridges. It 

 cannot be that this remarkable association is called for 

 merely as an aid to the sense of touch, for it does not occur 

 elsewhere on the skin, not even in its most sensitive parts. 

 Moreover, except on the " pad " areas, the ridges are in the 

 main arranged transversely to the long axis of the palm, sole, 

 and digits. They follow the same general plan on the hands 

 and feet of Quadrumana, and on the ventral aspect of the 

 tails of those of them whose tails are prehensile. 



Further, among Quadrumana, the ridges, with their inter- 

 vening furrows, are more distinct than in man, and the 

 patterns where they occur are simpler and present less 



