Abstract
The ponderal growth of the testes, with respect to body weight, has been studied from a series of 89 human fetuses, ranging from 16.3 to 3600 gm. in total body weight. 1 When the weight of the fetal testes is plotted against the weight of the body as a whole, it follows a rectilinear course which may be approximated by the expression:
where TW is the testes weight in gm., and BW is the total weight of the body in gm. This formula was computed from the individual values by the method of means. The calculated values thus obtained show a mean absolute deviation of 0.025 gm., and a mean relative deviation of 8.03% from the observed values. This relationship of the weight of the testes to total body weight is similar to that exhibited by the weights of many other organs and parts of the body in the fetal period.
In order to obtain the rate of growth, an age-testes weight formula was obtained by substituting the Scammon-Calkins body weight-age formula 2 in the testes weight-body weight formula equation (1), thus
Rate was calculated by obtaining the first derivative. The resulting rectilinear progression in rate is illustrated in Fig. 2.
The relation between testes-weight and body-length, as determined from 89 observations, is shown in Fig. 3. The empirical formula, determined from the averages of testes weight for 5 cm. intervals of body-length from 5 to 55 cm. inclusive (weighted by the square root of the number of observations in each interval) may be expressed as:
where TW is the testes weight in mg., e is the base of the natural logarithms, and BL is the total, or crown-heel body length. The mean, weighted, absolute deviation of the observed from the calculated means as determined by the above formula is 0.048 gm. and the corresponding relative deviation is 13.51%.
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