SECONDARY CHARACTERISTICS 19 



after this epoch for reproduction ; and lastly, and Pubescent 

 pathologically if the termination of life be pathological, J^^ 

 for producing changes which are associated with senility character- 



,7 . „ ,. i.i- istics and the 



— namely, the retention of lime salts in the tissues, metabolism. 

 especially in the arteries. There is no need to allude to 

 the many other important parts played by the calcium 

 salts in the human economy at all periods of life. It 

 must not, however, be thought that the thymus and 

 ovaries alone influence the calcium metabolism, for, as in 

 the metabolism of other elements, all the hormonopoietic 

 organs are concerned, either anabolically or katabolically. 

 And the same differences in regard to metabolic 

 conditions are found in many — perhaps all — directions 

 at the three essential periods of life which I have just 

 described. As a natural consequence, we find that the Functions of 

 functions of the organs of internal secretion differ not secretions 

 only at different periods of life, but normally in different 4lg e ^J *?_ 

 circumstances, such as those concerned with the inter- cumstances. 

 mittent reproductive functions of women ; and not 

 infrequently there is a coincidental alteration in structure, 

 such as is seen in the pituitary and thyroid during 

 pregnancy. Further work on these normal periodic 

 variations is urgently needed. 



The reproductive functions in Woman are dependent 

 on her specialized structures, both primary and 

 secondary ; and I have just endeavoured in a broad way 

 to show how structure and function are closely corre- 

 lated in producing the tout ensemble. 



To sum up. In early life — that is to say, before Summary in 

 puberty — the metabolism of girls is probably not very secondary 

 different from that of boys: the chemical processes of both character- 

 are for the most part engaged in promoting the growth 

 of the body. At puberty, however, a remarkable change 

 occurs, and it is at this period of life that the male 

 becomes most widely differentiated from the female. 



As we have seen, this further development is due to 

 the activity of the reproductive functions. In Woman 

 the change is shown by the psychical and physical 

 alterations which accompany the onset of menstruation. 



