44 ALE§ hrdliCka 



such estimates will be directly proportionate to the care with which 

 they are made and the experience of the one making them in that 

 direction. They are least reliable in childhood, and again in old age. 

 In arriving at his conclusion the observer is guided by the general 

 development and appearance of the subject ; by the eruption of certain 

 teeth, particularly the permanent molars; by marks of puberty and 

 climacterium; and by signs of aging such as grayness, wrinkling, 

 bending of the spine, loss and wear of the teeth, absorption of the jaws, 

 changes in sight and hearing, arcus senilis, clubbing of the fingers, etc. 

 But it must be borne in mind that none of these signs individually, 

 nor even in combination, can be taken as precise indices of age in years. 

 They develop at widely different ages in different individuals, and 

 even in the same person the setting in of the different signs of ageing 

 may be very irregular. Thus, grayness may occur even in young 

 adults, and the same is true of certain changes in the eyes and ears. 

 Moreover they do not appear synchronously or equally in the cultured 

 whites and other races. The student must be guided by the sum of 

 the manifestations, supplemented by the subject's behaviour and by 

 such indirect information (references to certain well known events, 

 etc.) as may be obtainable. But even thus and with ample experience 

 he cannot hope for closer approximation to the right age than within 

 five years; plus or minus, among adults. For anthropometric purposes, 

 however, such an approximation will be quite sufficient. 



Admixture of Blood. — Admixture of blood is of two main kinds: (1) 

 That between individuals of different tribes or other groups of the same 

 race ; and (2) That between individuals of different races. In general 

 the latter is the more important, and every effort must be made by the 

 investigator to detect individuals who bear such mixture and exclude 

 them from his series. This applies particularly when we deal with 

 mixtures of the three great stocks of mankind, namely the Whites, 

 the Yellow-browns, and the Blacks (Negro and Negrito). For the 

 sake of greater accuracy it would be well to speak of these great groups 

 always as "stocks" or "strains," reserving the term "races" for the 

 primary groups within these stocks — such as for instance the Nordics, 

 Alpines, and the Mediterraneans among the Europeans. 



The progeny of mixtures between individuals within the same stock 

 are often unrecognizable and cannot be separated except on the 

 basis of their family history. The progeny of mixtures of individuals 

 belonging to different stocks are in general easier to recognize, but 

 this facility differs according to the stocks concerned, for these are 



