NUMERICAL LAW OF REGRESSION OF CERTAIN SECONDARY SEX CHARACTERS.
The discrepancy in the relative variation of C and of theta led us to examine more closely the velocity of regression at the beginning in all the cases. At a given point of the curve, the velocity is furnished by the differential quotient of the length with reference to the time: See PDF for Equation At the beginning of regression, that is to say, at the time 0 See PDF for Equation We have tabulated the corresponding numerical values in the various instances: See PDF for Structure Although there is not absolute equality among the figures of the last column, one cannot fail to be struck by the fact that there is very little difference; in all instances they diverge much less than those of the first two columns, in which the variation is from 0.5 to 4.75 and from 1.95 to 12.0. We must admit, therefore, within rather wide limits, the constancy of the product of the time of regression and the constant C, whether the castration is intrapuberal or post-puberal. Geometrically, this result is represented by the constancy of the angle of the ordinate and the tangent to the parabola at the point of departure of the regression curve. Furthermore, it follows that the numerical law is represented not only by a parabola, but more exactly by segments of homothetic parabolas-an unexpected generalization, which gives a remarkable unity to the law with which it is concerned.
Pézard
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Laboratory of General Biology of the College of France, Paris.