CHAPTER XXIX 



REPRODUCTION 



IT is our purpose here to extend the account of the re- 

 productive process briefly outlined in Chapter III. In 

 the previous presentation it was stated that the body of 

 any one of the higher animals, including man, has grown 

 from a single cell, the fertilized ovum, by countless cleav- 

 ages. The statement has also been made that the fertil- 

 ized ovum is best viewed as a combination of two half -cells, 

 the fusion of which is the starting-point of the development 

 of a new generation. These two half-cells are contributed 

 by the two parents. The male is said to furnish the sperm 

 (or spermatozoon), and the 'union of this element with the 

 unfertilized ovum of the female is described as fertilization, 

 impregnation, or conception. 



The reproductive cells (for so we usually call them, 

 though we have said that they are more truly half-cells) 

 are detached from the gonads or reproductive glands in the 

 two sexes. These are the ovaries in the female and the 

 testes in the male. The ovaries of woman are small solid 

 masses of tissue, situated at the base of the abdominal 

 cavity, one on each side. The ova are gradually matured 

 in the ovaries, and from time to time released from the sur- 

 face of these organs. The number of the perfected ova pro- 

 vided is not great, perhaps 300 to 400 in a lifetime. This is 

 about the number of the menstrual periods, and it is roughly 

 true that the production of ova begins and ends with the 

 menstrual phenomenon; that is to say, it begins at about 

 fifteen and is ended at about forty-five years of age. But it 

 is not certain that there is a close coincidence between a 

 particular menstrual period and the liberation of an ovum. 



It is a singular fact that the ova are shed into the body 



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