532 Hepburn — The Papillary Ridges on the Hands and Feet of Monkeys and Men. 



In coming to the consideration of the eminences in the palm and sole, and the 

 arrangement of the papillary ridges upon them, I am of opinion that the produc- 

 tion of any special "design" or "pattern" is to some extent an accidental 

 occuiTence. In other words, the pattern is dependent upon such conditions as — 

 the particular shape assumed by each particular eminence, its rate of growth, and 

 any defects to which it may be liable — conditions which must be subject to con- 

 siderable variation, especially as we pass from monkeys whose grasping power 

 is practically essential to their safety, to man whose means of security and flight 

 from danger do not depend upon the grasping power of his hands and feet. 

 Consequently, I find among those which have come under my notice, that although 

 the monkey patterns are undoubtedly simpler and of less varied designs than the 

 patterns found in man, there is nevertheless a considerable amount of variety even 

 among them. 



Assuming that the shape and size of the eminences influence the pattern 

 constructed by the growth of the papillary ridges, it follows that the most freely 

 developed eminences will show the simplest forms of design, while, at the same 

 time, the nature of the design would be such as should assist the grasping power 

 by providing a surface capable of easy adaptation to the object grasped, and 

 one not likely to be readily displaced so long as pressm-e was maintained. 

 Now, the simplest form of eminence is one vnth a circular base and a free surface 

 rising very gradually to a flattened dome-like summit. As such a projection 

 grew, the pajDillary ridges would naturally tend to arrange themselves in a series 

 of more or less complete concentric circles, increasing in diameter from the centre 

 or summit of the eminence — which would be occupied by an extremely short 

 papillary ridge — practically a blunt point — or by a corresponding depression, 

 until at the base the concentric lines would be interfered with by ridges running 

 in other directions, and associated either with those of other eminences, or of 

 those intermediate areas already described. That such an arrangement does 

 actually occur may be seen by reference to PI. xlviii., in which the thenar emi- 

 nence and the eminence near the root of the little finger present marked instances 

 of the concentric arrangement of papillary ridges around one or two short central 

 rod-like ridges. Additional examples of this arrangement were seen in the hands 

 of the Egret monkey. 



The simplest modification of this fundamental pattern is seen on the three 

 eminences at the bases of the digits of the dog-faced baboon (PI. xlix.), in 

 the mandrill, and in Plate xlv., in all of which the large size and the flattened 

 summits of the eminences lead to a corresponding increase in the development of 

 the core, the result being the production of several short, almost longitudinal 

 ridges, bordered by a series of widening ellipses until the concentric circles are 

 finally produced. 



