CHAPTER XXX 

 EMBRYOLOGY 



Female organs of generation The ovaries Graafian follicles The parovarium The 

 uterus The Fallopian tubes Structure of the ovum Discharge of the ovum Passage 

 of ova into the Fallopian tubes Puberty and menstruation Changes in the Graafian 

 follicles after their rupture (corpus luteum) Corpus luteum of pregnancy Male organs 

 of generation Interstitial gland of the testis Vas deferens Vesiculae seminales Pros- 

 tate Glands of the urethra Male element of generation Spermatozoids. 



GENERATION is one of the most important of the animal functions and 

 as such usually is treated of quite fully in works on physiology ; but a 

 more or less extended account is also to be found in every complete 

 treatise on anatomy and in most works on obstetrics. The physiologi- 

 cal history of the human organism, however, would not be complete 

 without an account of generation and development ; although this will 

 involve, to some extent, a repetition of what usually is found in works 

 on other subjects. 



In what is known as sexual generation, the two anatomical elements 

 spermatozoid and ovum are developed in separate beings, male 

 and female, and are brought together, in man and in the higher animals, 

 by sexual connection, or copulation. In this way, the life of animals is 

 prolonged and individual forms are preserved in future beings. This 

 can not be secured without the acquisition by the ovum of a new ele- 

 ment. The animal cell may and does multiply by the process already 

 described under the name of karyokinesis ; but this can not continue in- 

 definitely. After a cell has undergone this process about one hundred 

 and fifty times, the reproductive power of the protoplasm, having gradu- 

 ally become enfeebled, is finally lost. It has been estimated that the cell 

 increases in mass by the appropriation of nutritive matters, as the cube 

 of its diameter, while the absorbing surface increases as the square of 

 the diameter (Herbert Spencer). If this view is accepted, it is evident 

 that a time will inevitably come in its life-history when the cell can no 

 longer absorb enough material for growth ; but with every division, there 

 is a relative increase in surface ; and thus it becomes possible for growth 

 to continue. The process of growth, indeed, might continue indefinitely 

 were it not that the cytoplasm gradually loses its power of appropriating 

 new matter. By the introduction of a new element, however, in the 

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