726 OF REPRODUCTION. 



Male children is 7 3 Ibs.: and that of Females 6-f Ibs. He adds that children which at the 

 full time weigh less than 5 Ibs. rarely thrive ; being generally feeble in their actions, and 

 dying within a short time. Several instances are on record, of infants whose weight at birth 

 exceeded 15 Ibs. It appears that healthy females, living in the country, and engaged in 

 active but not over-fatiguing occupations, have generally the largest children ; and this is 

 what might be expected d priori from the superior activity of their nutritive functions. 



949. Notwithstanding that, in any ordinary population, there is a decided 

 preponderance in the number of Females, the number of Male births is con- 

 siderably greater than that of females. Taking the average of the whole of 

 Europe, the proportion is about 106 Males to 100 Females. It is curious, 

 however, that this proportion is considerably different for legitimate and for 

 illegitimate births; the average of the latter being only 102 to 100, in the 

 places where that of the former was 105| to 100. This is probably to be 

 accounted for by the fact, which is one of the most remarkable contributions 

 that have yet been made by Statistics to Physiology, that the Sex of the off- 

 spring is influenced by the relative ages of the parents. The following table 

 expresses the average results obtained by M. Hofacker* in Germany, and by 

 Mr. Sadlert in Britain; between which it will be seen that there is a manifest 

 correspondence, although both were drawn from a too limited series of observa- 

 tions. The numbers indicate the proportion of Male births to 100 Females, 

 under the several conditions mentioned in the first column. 



Hofacker. Sadler. 



Father younger than Mother . . 9O6 Father younger than Mother . . 86-5 



Father and Mother of equal age . 9OO Father and Mother of equal age . 94' 8 



Father older by 1 to G years . . 103-4 Father older by 1 to 6 years . . 103-7 



6 to 9 . . . 124-7 . . 6 to 11 . . . 126-7 



9 to 18 . . . 143-7 . . 11 to 10 . . . 147-7 



18 and more . . 200-0 . . 16 and more . . 163-2 



From this it appears, that the more advanced age of the Male parent has a 

 very decided influence in occasioning a preponderance in the number of Male 

 infants ; and as the state of society generally involves a condition of this kind 

 in regard to marriages, whilst in the case of illegitimate children the same 

 does not hold good, the difference in the proportional number of male births 

 is accounted for. We are not likely to obtain data equally satisfactory in 

 regard to the influence of more advanced age on the part of the Female parent ; 

 as a difference of 10 or 15 years on that side is not so common. If it exist 

 to the same extent, it is probable that the same law would be found to prevail 

 in regard to Female children born under such circumstances, as has been 

 stated with respect to the Male; namely, that the mortality is greater during 

 embryonic life and early infancy, so that the preponderance is reduced. 



950. There appears to be, from the first, a difference in the viability (or 

 probability of life) of Male and Female children ; for, out of the total number 

 born dead, there are 3 Males to 2 Females : this proportion gradually lessens, 

 however, during early infancy ; being about 4 to 3 during the first two months, 

 and about 4 to 5 during the next three months; after which time the deaths 

 are nearly in proportion to the numbers, of the two sexes respectively, until 

 the age of puberty. The viability of the two sexes continues to increase 

 during childhood ; and attains its maximum between the 13th and 14th years. 

 For a short time after this epoch has been passed, the rate of mortality is 

 higher in Females than in Males ; but from about the age of 18 to 28, the 

 mortality is much greater in Males, being at its maximum at 25, when the 

 viability is only half what it is at puberty. This fact is a very striking one ; 

 and shows most forcibly that the indulgence of the passions not only weakens 

 the health, but in a great number of instances is the cause of a very premature 



* Annales d'Hygiene, Oct. 1S29. f Law of Population, vol. ii. p. 343. 



