INFLUENCE OF RACE AND SEX ON GHOWTtt-PliOCESS 487 

 In the autocatalytic formula as applied to the process of growth: 



log = ka(t - ti) 



a x 



the constant "a" is proportional to some exponent of the concentration 

 of growth-substrates, i. e., to the Nutrient-level. In any given species, 

 therefore, we may expect to find that within certain limits its magnitude 

 is affected by the environment and especially by the abundance or 

 paucity of the dietary. The constant " k" on the contrary is expressive 

 of the specific velocity of the process of tissue-disintegration, charac- 

 teristic of the species,, probably of the sex, and peculiar even to a 

 particular individual. Thus we may expect, in a given species, to find 

 that its magnitude is unaffected by the environment, but dependent 

 upon Sex and Race. We have seen that the autocatalytic formula 

 applies to the first nine months of extra-uterine growth in infants and 

 that the values of "a" and "k" may be computed from all of the 

 observed weights at the various ages chosen for the comparison of the 

 equation with the results of actual measurement. In the following 

 table the values of "a" and "k" for British Infants born in England 

 and in Australia respectively and for South German infants born in 

 Frankfurt (from the data of Schmidt-Monnard) are compared: 



COMPARISON OF THE EFFECTS OF RACE AND ENVIRONMENT UPON THE 

 PARAMETERS OF THE GROWTH-CURVE. 



Males. Females. 



Race and place of birth. a (ounces). kxlO 6 . a (ounces). kxlO 6 . 



British (born in England) . . 318 399 312 340 



British (born in Australia) . : 341.5 398 350 317 



South German ..... 315 451 290 537 



It will be seen that the parameters or constants of the growth curve 

 of infants are affected in the sense indicated by the above discussion 

 by the factors of sex, race and environment. While the value of "a" 

 is not greatly affected by sex or by dissimilarity of race, the values 

 obtained in the similar environments of Frankfurt and London being 

 very alike, it is greatly affected by dissimilarities in environment, as a 

 comparison of the values of " a" in Australia and in Europe shows. On 

 the other hand, "k" is comparatively unaffected by environment, being 

 practically identical for British males, whether born in Australia or in 

 England, and very nearly the same for British females born in these two 

 environments, whereas it is profoundly affected in magnitude by sex 

 and race, as indicated by the marked difference in the values of "k" 

 for males and females and for South-German as compared with British 

 infants. 



When it is remembered that these parameters have not been calcu- 

 lated arbitrarily, but that they are computed by the method of least 

 squares from all of the observations and therefore partake in some 

 measure in the errors incident to the observations, it will be seen that 



