HE differences between men and women in relation to the processes that lead to death are of more than passing interest for the student of human constitution. This branch of human biology, it has been emphasized (Pearl and Ciocco, I936; Ciocco, I936a, b), has for one of its major objectives to discover and eventually measure the stable organic correlationintegrated biological relations-between the morphological, physiological, psychological, and pathological traits of the individual. Therefore, the differences in morbidity and mortality observed for the two sexes assume special importance not only because the individuals of the two sexes are on the whole also morphologically and functionally differentiated but primarily because the sex dimorphism reflects a dissimilar biological make-up. This, it is of course realized, does not mean that sex differentiation is due simply to the chromosomal constitution of the individuals. In the first place, as Danforth (I93z) ably points out, the results of investigations on sex linkage have shown clearly that the so-called sex chromosomes are, one might say, only incidentally concerned with sex differentiation. Besides, as a result of the work of Bridges and of all those who have confirmed and extended his observations (Bridges, I932), it is accepted that the characteristics of each of the sexes are deternmined not only by the absence or presence of one of the sex chromosomes but also by the quantitative balance between the number of sex and autosomal chromosomes. The original simple scheme is further relegated into the background when an explanation is sought for Goldschmidt's observations on the alteration of the sex ratio and on the production of intersexes as the result of crosses between certain varieties of tussock moths. The conclusion which Goldschmidt (I9I7) reached and which he has maintained since (cf. Goldschmidt, I938), is that "every individual is -able to develop into one sex or the other or any stage between; further that every individual contains all the elements necessary for the development of either sex and its attributes; further that these elements or substances must have a certain quantitative relation to each other in order to secure to one of them the control of development; and that the introduction of quantities in a cross which do not fit the given quantity of the other partner set up the sex differentiation in favor of the higher quantity." That the final differentiation of sex is dependent also on extra-chromosomal factors is universally admitted today, thanks to the many observations and experimentations reported on gynandromorphism and sex reversal. Thus, the observation by Crew (I973) of the broody hen transformed through disease into a potent rooster is well known. Equally familiar are the studies of Hertwig (I906) continued and elaborated further by
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