HORMONES 
25 
their full development, as is done in very early marriage, is a 
serious mistake. 
1. Why is the beginning of adolescence called “puberty”? 
2. What changes of sex organs occur at puberty? 
3. What change of relationship between boys and girls occurs at 
this period? 
4. Why are not boys and girls suited for marriage as soon as their 
sex organs begin to function ? 
Hormones. — The strength and beauty of the adolescent 
growth is caused by the development of the sex organs. As 
the ovaries in girls become larger at puberty, certain cells in 
them begin to secrete a hormone (hor'mone), a substance 
which is absorbed by the blood and carried to all parts of the 
body. The hormone stimulates the rapid growth character¬ 
istic of this age and molds the awkward girl into a beautiful 
womanly form. It also acts on the brain and causes the mind 
to develop its characteristic traits. Without this secretion 
by the ovaries the perfect woman does not develop. 
In the boy there is a corresponding hormone secreted by 
certain cells of the testis, called intersti'tial cells because they 
lie in the interstices or spaces between the sperm-producing 
cells. When this hormone is absorbed and carried through¬ 
out the body, it causes the growth of the manly frame and 
inspires the courageous spirit. Without this secretion the 
body and mind do not acquire their full vigor. It is, there¬ 
fore, of the utmost importance that these secreting reproduc¬ 
tive organs be kept in perfect health. 
The gland grafting that we sometimes read about in the 
papers consists in grafting a part of a testis from a young man, 
or sometimes from another animal such as a goat, into the 
body of an old man. The thought is that the interstitial 
cells of the grafted gland will produce their hormone in the 
old man, whose testes have ceased to function, and in this way 
give him renewed vigor. In some cases the operation seems 
