Chapter 2 



Structure and Function of Organs and Tissues 

 as Criteria of Individuality 



Our recognition of and distinction between different human indi- 

 | viduals depends on many factors, particularly on their facial features, 

 the color of hair and eyes, the height and outlines of their bodies, the 

 character of their movements, especially their way of walking, the quality of 

 their voices and modes of speech, thinking and feeling, in general on their 

 reactions under varying conditions. By these means we can distinguish be- 

 tween individuals and we conclude that no two persons whom we meet are 

 exactly alike ; this holds good even of identical twins. But a certain experience 

 is necessary in the use of these different signs. We can best differentiate 

 individuals who, in the most essential features, are similar to those we meet 

 daily in the greatest number, and we have more difficulty in differentiating 

 between classes of individuals with which we are less well acquainted ; for 

 instance, it is more difficult for most of us to distinguish between individual 

 monkeys and dogs, than between human beings, although persons who are 

 studying monkeys and dogs very closely can, here, also quite readily distin- 

 guish different individuals. We use the combination of a large number of 

 organ and tissue peculiarities and the general body build as distinguishing 

 marks between individuals, each individual thus representing to us a mosaic, 

 which, as a rule, leaves in us a composite impression rather than a memory of 

 the separate elements constituting the mosaic. These separate features are 

 determined largely by inheritance, although variable environmental factors 

 may greatly influence their ultimate character, and different kinds of charac- 

 teristics are unequally affected by the genetic constitution of the individual 

 and by environmental factors, the experiences through which the individual 

 has passed. 



We shall discuss here, in particular, two characteristic features which 

 distinguish human individuals and which are especially striking as to their 

 fineness of individualization, namely, the skin patterns, which are employed 

 for the identification of individuals, and the scents which dogs use in tracing 

 the movements of and in recognizing individuals. 



I. The palmar and plantar skin patterns as criteria of individuality. The 

 patterns due to the arrangements of the ridges in the skin of the palms of 

 the hand and the plantar surfaces of the foot differ, but are constant in each 

 individual; in the form of finger prints they are used to distinguish indi- 

 viduals from one another. These peculiarities are distinct from the indi- 

 viduality differential, inasmuch as they are limited to one particular organ 

 and do not represent a characteristic shared by all or the majority of the 

 organs or tissues of the body. In this respect they resemble therefore other 



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