ARRANGEMENTS OF THE PAPILLARY RIDGES 167 



can be created and disposed in their lines by pressure, friction and 

 response, The clearest case is one I brought forward at the 

 Zoological Society of London in 1905, and which was published in 

 its proceedings of April 18th. It was an instance of the hand of a 

 chimpanzee with papillary ridges produced in an aberrant or 

 abnormal situation by walking, and was given as follows : — 



" In the course of an examination of the papillary ridges 

 in some specimens of anthropoid apes and monkeys certain 

 groups of ridges were found on the extensor surface of the 

 terminal phalanges of the hand, apparently identical with 

 those of the palmar and plantar surfaces. Three specimens 

 of chimpanzee living in the Society's menagerie were examined, 

 of the ages : one year eight months, two-and-a-half years and 

 six years. In the oldest of these, called " Mickie," the ridges 

 were definite and well -developed, on the second, third and 

 fourth digits on both hands ; in the youngest specimen, " Jack," 

 they were absent ; and in " Jimmie," two -and -a -half years 

 old, they were small and ill-defined, as if in process of 

 development. 



Direction of Ridges. 



Mickie. Ridges longitudinal and reaching to the matrix of 



the nail on the second, third and fourth digits. 

 Jimmie. Showed ridges as follows : — 

 R. hand 1st D none L. hand 1st D none. 



2nd ,, oblique 2nd „ oblique. 



3rd ,, transverse at base of D. 3rd ,, 



4th ,, ,, „ „ 4th „ 



5th ,, nearly longitudinal. 5th ,, none. 



In these three specimens ridges were absent from the corre- 

 sponding surfaces of the foot. 



' The well-defined longitudinal direction of the ridges 

 in '' Mickie " is worth notice. It must be remembered in 

 this connection that a chimpanzee walks with the extensor 

 surfaces of the phalanges touching the ground and the digits 

 turned inwards, so that their long axis are at right angles to 

 the line of progression of the animal, and accordingly the ridges 

 of this part also occupy the same relative position. There is 

 no correlation in this instance between the act of prehension 

 and the direction of the ridges, though it agrees closely with 

 the general rule which obtains in so many regions, that the 

 ridges lie at right angles to the line of incidence of the 

 predominating pressure on the part." 



