July 6, 1917] 



SCIENCE 



21 



site sex. Wtile the chromosomal correlation is 

 here forced to failure the metabolic correla- 

 lation here persists. The chromosomal consti- 

 tution is not an efficient cause of sex; it is but 

 a sign or index'' and possibly an assistance in 

 the normal maintenance of that which is es- 

 sential — namely, two different metabolic levels. 

 But the requisite metabolic level of the germ 

 may be established in the absence of the usual 

 or appropriate chromosome complex, and the 

 sex of the offspring made to correspond to the 

 acquired grade or level of metabolism. 



These facts which we consider firmly estab- 

 lished in the pigeons carry the further essen- 

 tial analysis of sex practically into the field of 

 physiology and bio-chemistry. Further analy- 

 sis of the basis of sexual difference — in germ 

 or in adult — is to be sought in studies of the 

 metabolic differences of the two kinds of sex- 

 germs, of adults of the two sexes, and of in- 

 dividuals of intermediate sex. ISTow that the 

 problem of sex has been shown to belong in the 

 field of metabolism we shall be able to note, in 

 connection with our diagram, that a number of 

 the requisite data bearing on germinal and 

 adult sexual differences are already at hand. 



Turning now to the diagram we note that 

 egg and aduU stages are considered. In the 

 egg of the pigeon we have identified maleness 

 and f emaleness by three differentials. Female- 

 ness in the egg stage being accompanied by 

 low metabolism, lower percentage of B1,0, and 

 higher total fat and phosphorus, or of phos- 

 phatides. Maleness is here accompanied by 

 high metabolism, higher percentage of water, 

 and lower total fat and phosphatides. Now 

 there are valid reasons for treating these three 

 differentials not as absolutely separate and dis- 

 connected facts, but rather as aspects or cor- 

 rollaries of the same fact. For example, a 

 high metabolism in a cell is consonant with 

 less storage of fat and phosphatides, and with 

 a more highly hydrated state of the cell-col- 

 loids. It follows that where data for either of 



* Since the chromosomes are structural charac- 

 ters they can not be expected readily to alter their 

 numbers, etc., in response to new quantitative lev- 

 els attained (permanently) by the fundamental 

 cell-functions. 



these three differentials are at hand, for either 

 the germ or adult of any animal, we have in 

 such data evidence of the kind we are looking 

 for, i. e., evidence for the association of a 

 given type of metabolism with the germ or 

 adult of a given sex. 



TABLE I 



Sexual Differences of Fat and Phosphorus in the 

 Blood of Adult Fowls and Man 



For what forms then are such data available? 

 And, what is now known of the persistence of 

 this definite type of differentiation of the two 

 kinds of sex -germs into adult stages of the two 

 sexes? Recently Lawrence and Riddle^ have 

 shown that one of these differentials — or one 

 aspect of the differential which my own work 

 has demonstrated in the egg — is clearly con- 

 tinued in the blood of the adult male and fe- 

 male (see Table I.). Fowls were substituted 

 for doves in this case in order to increase the 

 size of the sample, and thus increase the ac- 

 curacy of the analytical results. In birds, 

 therefore, we have fairly clear evidence that 

 the metabolic differences of male and female 

 germs persist in the male and female adults. 

 In mammals too these aspects of sexual differ- 

 ences of the adults have been fully demon- 

 strated. Almost simultaneously with the 

 above determinations, data were published by 

 Goettler and Baker," which as we have pointed 

 out, show that the blood of the human male 

 contains less fat, that of the female more.^ 

 Further, the basal metabolism of the human 

 male and female has recently been accurately 



5 ' ' Sexual Differences in the Pat and Phos- 

 phorous Content of the Blood of Powls," Amer. 

 Jour, of Phys., Vol. XLI., September, 1916. 



6 Jour. Biol. Chem., XXV., June, 1916. 



'' This result seems to have been anticipated by 

 Gorup-Besanez in 1878. 



