354 



THE INTERNAL ENVIRONMENT OF THE BODY 



Part III 



OVARIAN 

 CYCLE 



UTERINE 

 CYCLE 



Functional 

 layer of 

 mucosa 



Basa! 

 layer 



Day of cycle 



Unfertiliied 



ovum,- 



Ovum 

 fertilized and 



Regressing Corpus 



^ de-geneVates i^r^J^X, ^^**"'" ^ implanted.- . 



" * ^^ If '^fS^, XSJ^ corpus luteum persisfs 



Corpus tuteum 



of Pregnancy 



V4„; 



OVULATION 



IMPLANTATION 



Copid qrowlh of 

 follicle ending 

 in ovulation 



Migration and deolh rCBTILIZATION , 

 of ovum. Funclionol 

 corpuJ luleum OVULATION 



PLACLNTATION 



(Ovulolion ceasei. 



Corpus luleum 



conlinuej) 



Menses Proliferative 

 Phase 



Secretory Phase 



Incomplete cycle 



Placentation 

 (Menses Withheld) 



ORDINARY MENSTRUAL CYCLE 



MENSTRUAL CYCLE ENDING IN PREGNANCY 



Fig. 18.15. Graphic summary of changes in the inner layers (endometrium) of 

 the uterus in an ordinary menstrual cycle and in another cycle in which pregnancy 

 occurs. The changes in the ovary are placed in their proper relation to the time 

 scale and activities in the uterus. (Courtesy, Patten: Human Embrvology, ed. 2. 

 New York, The Blakiston Co., 1953.) 



Production of Children 



Production is important to the human crop as it is to others How can pro- 

 duction of children be encouraged when there is plenty of space and food and, 

 what is more difficult, discouraged when there is not? These two questions 

 penetrate into every society the world around. 



Behind both questions is the fact that living matter insists upon reproducing 

 itself. The many cells of our bodies are due to their persistent multiplication. 

 Hard or easy living, much or little food, heat or cold may affect reproduction, 

 but in general and in the long run they do not stop it. Children were conceived 

 and born in the worst prison camps of World War II. 



The problem of inducing production of children is a complex one that for 

 thousands of years has been met according to the understanding of various 

 peoples. Social and economic influences are exceedingly important and they 

 as well as the physiological ones are very complex. In our own time, the gen- 

 eral trend of experimental evidence has shown that the sperm and egg are 

 capable of fertilization for a shorter time than was previously supposed. 



The problem of reducing the production of children is also an old one, 

 dealt with in ancient times and in primitive societies. Fundamentally, it is 

 solved by preventing the egg and sperm cells from meeting. Almost all animals 

 do this for a good part of their lives because they only mate at certain sharply 



