PROPORTION OF SEXES. 



727 



death. From the age of 28 to that of 50, the mortality is greater, and the 

 viability less, on the side of the Female ; this is what would be anticipated 

 from the increased risk, to which she is liable during the parturient period. 

 After the age of 50, the mortality is nearly the same for both. 



a. These facts have been expressed by Quetelet in a form which brings them prominently 

 before the eye (Fig. 289). The relative viability of the Male at different ages is represented 

 by a curved line; the elevation of which indicates its degree, at the respective periods 

 marked along the base line. The dotted line which follows a different curve, represents 

 the viability of the Female. Starting from a, the period of birth, we arrive at the maxi- 

 mum of viability for both at b ; from this point, the Female curve steadily descends towards 



Fig. 2S9. 



Diagram representing the comparative Viability of the Male and Female at different Ages. 



n, at first very rapidly, but afterwards more gradually; whilst the Male curve does not de- 

 scend quite so soon, but afterwards falls much lower, its minimum being c, which corresponds 

 with the age of 25 years. It afterwards ascends to d, which is the maximum of viability 

 subsequently to the age of puberty; this point is attained at the age of 30 years, from which 

 period, up to 50, the probability of life is greater in the Male than in the Female. In the 

 decline of life there seems little difference for the two sexes. 



951. Similar diagrams have been constructed by Quetelet, to indicate the 

 relative Heights and Weights of the two sexes (Fig. 290). 



a. In regard to Height it may be observed, that the increase is most rapid in the first 

 year, and that it afterwards diminishes gradually; between the ages of 5 and 16 years, the 

 annual increase is very regular. The difference between the Height of the Male and Fe- 

 male, which has been already stated to present itself at birth, continues to increase during 

 infancy and youth; it is not very decided, however, until about the 15th year, after which 

 the growth of the Female proceeds at a much diminished rate, whilst that of the Male con- 

 tinues in nearly the same degree, until about the age of 19 years. It appears, then, that the 

 Female comes to her full development in regard to Height, earlier than does the Male. It 

 seems probable, from the observations of Quetelet, that the full height of the Male is not 



