The first principles of heredity; with 75 illustrations and diagrms . •be. 10 20 30 ^ 30 60 70 80 90 100 Fig. 62.—Diagram of Strength of Pull. (After Galton.) medium strength of pull, and that the curve graduallyslopes down towards both ends. If we have more exact measurements from a greaternumber of people, the curve becomes a more regular flowingone, as in Fig. 63, where variations in stature are repre-sented, the result of 4,426 measurements of members ofCambridge University of British extraction, recorded bythe Cambridge Anthropological Society. The base linegives the stature in inches, th
The first principles of heredity; with 75 illustrations and diagrms . •be. 10 20 30 ^ 30 60 70 80 90 100 Fig. 62.—Diagram of Strength of Pull. (After Galton.) medium strength of pull, and that the curve graduallyslopes down towards both ends. If we have more exact measurements from a greaternumber of people, the curve becomes a more regular flowingone, as in Fig. 63, where variations in stature are repre-sented, the result of 4,426 measurements of members ofCambridge University of British extraction, recorded bythe Cambridge Anthropological Society. The base linegives the stature in inches, the vertical line the number ofindividuals exhibiting the different heights of the continuous line going through the points ofmeasurements plotted out in the diagram represents verynearly a curve, which is identical with what is called in 19 146 THE FIRST PRINCIPLES OF HEREDITY mathematics the Normal Curve of Frequency of Error,or, shortly, the Normal Frequency Curve/ reoo lndi\/iduiL!s. 62 63 64 65 66 Stature In Inches, 67 68 69 70 71 72 73 74 76 76 Fig. 6^.—Curve of Stature. {From R. H. Lock, Recent Progress in the Study of Variation, Heredity, and Evolution.) In order to comprehend what the Normal FrequencyCurve stands for, we must enter somewhat into the fieldof the mathematical theory of probability.* If we tossup two similar coins simultaneously there are three possi-bilities : We may get head-head (H-H), head-tail (H-T),or tail-tail (T-T). When tossing up the coins a very greatnumber of times, we find that, according to the Law ofProbability, we get head-tail twice as often as eitherhead-head or tail-tail. We get, in fact: I H-H + 2H-T+1 T-T. (This is due to the fact that in tossing up thetwo coins many times—, fifty times—we throw up * We can give only the very briefest account of this subject,which is mathematical and very abstract, and shall also in thefollowing pages state only the most essential facts of Biometrics,seeing that this science i
Size: 2205px × 1133px
Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, bookpublisherlondo, bookyear1910
