158 Dr. D. C. L. Fitzwilliams on the 



broadest, and least arched, it most closely resembles the 

 human nail. As one approaches the little finger the nail of 

 each digit becomes successively longer, narrower, more arched, 

 and therefore more claw-like, in a manner analogous to that 

 noted by Wiedersheim in the human hand. This is due to 

 the greater and more varied use to which the nails of the 

 outer digits are put ; that of the little finger, being the least 

 used, retains in a greater degree than the others its primitive 

 claw-like character. 



The fine lines on the palmar skin are much coarser than 

 those on the human hand, and in many cases pass inter- 

 ruptedly across the deep creases of the palm. 



The coarseness of the finer lines is probably a response to 

 the requirements of function : the animal uses its hands as 

 hooks by which to suspend the weight of the body from the 

 branches, and the friction produced by the finer lines gives 

 firmness to the grip. If the skin of the palm were devoid of 

 lines and perfectly smooth a firm grip, with no slipping, 

 would be difficult to obtain. The delicacy of the lines of the 

 human hand is due to the fact that the hand is no longer an 

 organ merely of grasp, but used for many varied and highly 

 specialized movements. 



In the gibbon the lines are arranged in a definite manner 

 and one well calculated to obviate the risk of the hand 

 slipping from a branch. In the lower part of the palm the 

 lines show a general tendency to converge towards the central 

 digit. In the fingers the lines are arranged in a chevron-like 

 manner, converging from the margins downwards towards 

 the longitudinal crease which runs along the centre of each 

 digit. This arrangement is best seen on the proximal and 

 middle phalanges of the third and fourth digits, where the 

 weight of the body chiefly rests. The lines of the proximal 

 and middle phalanges of the second and fifth digits, like the 

 lines of the palm, have a tendency to converge towards the 

 central digit. This tendency survives in the human hand 

 only on those parts which are used solely for grip and not for 

 the execution of any of the finer movements. It is well seen 

 on the palm near to, and on the proximal phalanges of, the 

 index and little fingers, whilst elsewhere the lines run in an 

 irregular manner, forming whorls and triangles which diflfer 

 in individual hands. This wonderful difference in the 

 patterns met with on the thumb is used by the police in the 

 identification of criminals. 



Oblique lines are found to be more efficient mechanical 

 agents for the prevention of slipping than transverse. For 



