. Preventive medicine and hygiene. d with peasor similar objects. Below this is a regular series of obstacles symmetri-cally arranged, and at the bottom of the board is a row of vertical com- 494 HEEEDITY AND EUGENICS partments also arranged symmetrically with reference to the chief axisof the whole system. If we allow the peas to run through the funneland fall among the obstacles into the compartments below, we find thattheir distribution will follow certain laws capable of precise mathe-matical description. The distribution of the peas may be predictedwith fair accuracy. The middle compartme
. Preventive medicine and hygiene. d with peasor similar objects. Below this is a regular series of obstacles symmetri-cally arranged, and at the bottom of the board is a row of vertical com- 494 HEEEDITY AND EUGENICS partments also arranged symmetrically with reference to the chief axisof the whole system. If we allow the peas to run through the funneland fall among the obstacles into the compartments below, we find thattheir distribution will follow certain laws capable of precise mathe-matical description. The distribution of the peas may be predictedwith fair accuracy. The middle compartment will receive the most;the compartments next the middle somewhat fewer; those further fromthe middle still fewer; and the end compartment fewest. If we connectthe top of each column of peas by a curved line we get a curve knownas the normal frequency curve. A curve of the same essential char-acter would result from plotting the dimensions of a thousand cobble-stones, the deviation from the bulls eye in a target-shooting contest,. Q M Q Fig. 66.—Normal Curve. (Lock.) or by plotting the variability of a biologic character, such as the statureor strength of men, the spread of sparrows wings, the number of rayson scallop shells, or of ray flowers of daisies. While from the above law of probability we know quite definitelywhat the general distribution of the peas will be, we do not know atall the future position of any single pea. Of this we can speak only interms of probability. The chances are very high that it will fall inone of the three middle compartments, very low that it will be one ofthe extreme compartments. The chances are equal that any individualpea will fall above or below the average or middle position. We there-fore see that in any group there are many more individuals near theaverage than there are in the classes removed from the average, andthe farther the removal of a class from the average the smaller thenumber of individuals in that class; hence, we have the
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Keywords: ., bookauthorwh, bookcentury1900, bookdecade1910, booksubjecthygiene
