76 TABOO AND GENETICS 



lactation. Until puberty, when sex ceases to 

 be merely potential and becomes functional 

 (about 12-14 ii^ girls and 14-16 in boys), the 

 differences in metabolism are not very marked. 

 Neither are they in old age, after sex has ceased 

 to be functional. It is during the period when 

 sex is functional (about 35 years in women and 

 considerably longer in men) that the gross 

 physiological differences manifest themselves. 



Before puberty in both sexes, calcium or lime 

 salts are retained in the tissues and go to build 

 up the bony skeleton. (A mere sketch of 

 calcium metabolism is all that can be given here 

 — for details consult such works as 15 and 17 

 in bibliography ; summary in 14 ; pp. 34f. & 

 i6if.) Note that puberty comes earlier in 

 girls than in boys, and that the skeleton there- 

 fore remains lighter. During the reproductive 

 period in women these salts are heavily drawn 

 upon for the use of the reproductive system. 

 The male reproductive system draws upon them 

 as well, though the drain is very slight as com- 

 pared to that in women. In old age these salts 

 produce senility through deposit in the tissues, 

 especially in the arteries. 



At the pubertal age in girls begins the 

 phenomenon known as menstruation, in which 

 there is a large excretion of calcium salts. In 

 pregnancy these are needed for building the 

 skeleton of the foetus, and at delivery go to the 



