PALM AND SOLE STUDIES. 235 



of generations, with its beginnings somewhere in the Simian line, 

 the individuals of which, though with many a retrogression, have 

 progressed steadily from a series of complicated patterns, de- 

 veloped in association with raised pad organs, to a simple con- 

 dition of parallel ridges, more or less conformable to the principal 

 lines of flexure. 



Expressed in another way, the results of the study of friction- 

 ridges, especially in connection with their possible heritability, 

 may be collected into a series of definite statements, as follows: 



I. Each friction-ridge pattern presents, by taking a large 

 number of human individuals, every stage in the process of 

 development, from a whorl of concentric lines with a definite 

 number of embracing triradii, to a condition in which core 

 and triradii are completely lost and the surface is covered by 

 simple parallel ridges, straight or slightly curved. 1 



II. From comparative study of other Primates it is plain 

 that the course of evolution has been from the involved condition, 

 the whorl, which is distinctly Simian, through every stage in the 

 reduction of the pattern, to its final complete effacement. 2 



III. A given pattern shows as a rule more than one way in 

 which it may degenerate, often two or three, and each way may 

 be shown by complete series of instances taken from individual 

 cases, and leading to the same final result. 3 



IV. The ridges forming a given pattern are first seen in an 

 embryo of approximately four months, since w T hich age there is 

 no indication of change throughout life. This has been absolutely 

 proven in the case of individuals after birth by separate observa- 

 tions taken upon the same person, and in a number of instances 

 these observations have been separated by a period of fifty or 

 more years; in the embryo the ridges appear in a definite form, 

 and there is no indication of later modification or of provision for 

 it. 4 



1 Miss Whipple, 1904. 

 " Miss Whipple, 1904. 



3 Miss Whipple, 1904, pp. 343-354- 



4 The occurrence of ridge rudiments, occasionally found lying between normal 

 ridges, and reduced often to broken lines without sweat-pores, suggests the pos- 

 sibility that in an early embryonic stage these may have been as large as the 

 others, and that they may have become pushed out of existence, or suppressed, 

 owing to some mechanical pressure during ontogeny. Of this we have no proof, 



