Differential growth of human foetal gonads with respect to sex and body side.

Measurements have been carried out on the gonads of 54 human foetuses, 29 males and 25 females. Crown-rump lengths ranged between 140 and 212 mm. The criteria used were fresh weight, total protein contents and total DNA contents. It was found that for any given crown-rump length class, the mean values of testes exceeded those of ovaries for all three criteria. It was also found that the mean values of right gonads exceeded those of left gonads. Since in true hermaphrodites, testes are preferentially situated on the right and ovaries on the left side, it is concluded that there is a causal relationship between increased growth rate and testicular differentiation. It is suggested that in normal development this function is performed by the Y chromosome.