PROPORTION OF THE SEXES. 



625 



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

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

 before the eye (Fig. 188). 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 maximum of viability for both at 

 /; ; from this point, the Female curve steadily descends towards n, at first very 

 rapidly, but afterwards more gradually ; whilst the Male curve does not quite 

 descend 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. 



Fig. 188. 



Diagram representing the comparative Viability of the Male and Female at different ages. (After Quetelet.) 



773. Similar diagrams have been constructed by Gluetelet, to indicate the 

 relative Heights and Weights of the two sexes (Fig. 189). 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 1(> 

 years, the annual increase is very regular. The difference between the 

 Height of the Male and Female, 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 continues 

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