968 



OF GENERATION EMBRYONIC DEVELOPMENT. 



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 par- 

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

 both. These facts have been expressed by Quetelet 1 in a form which brings 

 them prominently before the eye (Fig. 365). 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 n, at first very rapidly, but afterwards more gradually ; 

 whilst the male curve does not descend quite so soon, but afterwards falls 

 much lower, its minimum being e, which corresponds with the age of 25 

 years. It afterwards ascends to d, which is the maximum of viability sub- 

 sequently 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 or no differ- 

 ence for the two sexes. 



FIG. 366. 



iei&htaf 



of 



Neidlii of 



o #/ 



Male 



Male 



_ - 

 'e turtle 



.5 10 JJ 20 2.5 ;n> JO :'>0 C,0 f tO 



Diagram representing the Comparative Heights and Weights of the Male and Female at different Ages. 



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

 relative Heights and Weights of the two sexes at different ages (Fig. 366). 

 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 be- 

 tween 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 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 obser- 



Op. cit. 



