EMBRYO LIFE 
21 
the vagina. The thousands of spermatozoa, moving blindly 
about, swarm over the moist lining of the vagina and uterus. 
Many of them work up the uterine tubes, ready to meet the 
egg when it leaves the ovary. They may live in the uterus 
and tubes for a week or two. 
If the egg is fertilized, it lodges in the uterus and grows. 
This process is called conception . Since only one of the 
thousands of spermatozoa is needed to fertilize the egg, con¬ 
ception will probably occur if any sperm cells are present. 
If the egg is not fertilized, it remains only a short time in the 
uterus and is then discharged. 
1. What is the function of the female? 
2. Where are the ovaries ? 
3. How frequently does ovulation (the discharge of a mature egg) 
occur in human beings ? 
4. How are the eggs conveyed to the uterus ? 
5. What is the uterus ? 
6. How do the spermatozoa get to the eggs ? 
7. What is meant by conception ? 
8. Why will conception probably occur from sexual intercourse 
at any time of the month? 
Embryo Life. — We learned on page 15 that the large eggs 
of reptiles and birds are stored with food to supply the grow¬ 
ing embryo until it is well developed and ready to come out 
into the world, and also that the oxygen needed by the em¬ 
bryo is obtained by means of a respiratory membrane under 
the shell. We shall now see how the mammals better pro¬ 
vide for their developing young. Mammals produce eggs so 
small as hardly to be visible, about one hundredth of an inch 
in diameter. The fertilized egg, as also the embryo which 
develops from it, is retained within the uterus, protected, 
warmed, nourished, supplied with oxygen, and its wastes 
removed until it is grown and ready for birth. The embryo 
or foetus (fe'tus) receives its supplies through the mother’s 
blood in the following manner: 
