CHAPTER XII. 



THE OVUM AND OVTJLATION. 



Structure of the ovum Vitelline membrane Yitellus Germinal vesicle and 

 germinal spot Discharge of the ovum Passage of ova into the Fallopian 

 tubes Puberty and menstruation Description of a menstrual period 

 Characters of the menstrual flow Changes in the uterine mucous mem- 

 brane during menstruation Changes in the Graafian follicle after its rupture 

 (corpus luteum) Corpus luteum of pregnancy. 



have now to study, as a necessary introduction to the 

 history of development, the structure of the ripe ovum, the 

 mechanism of its discharge from the Graafian follicle, and 

 the phenomena which attend the process of ovulation. . 



Anterior to 1827, there was much discussion among physi- 

 ologists, with regard to the production, discharge, etc., of the 

 female element of generation. In 1827, Yon Baer distinctly 

 described the ovum in man and mammals, noted its relations 

 to the Graafian follicle, concerning which there had been great 

 confusion, and designated it as the veritable ovum, destined 

 to be developed into the foetus. 1 From this description, Yon 

 Baer is regarded as the discoverer of the human ovum ; not 

 so much because he was the first to see it, for imperfect 

 descriptions of the ovum had been given, in rabbits, dogs, 

 etc., many years before, but for the reason that his descrip- 

 tion was the most accurate, and settled several important 

 points of dispute. 



1 DE BAER, Lettre sur la formation de Vc&uf dans Vespece humaine et dans les 

 mammiferes. Publiee par G. BRESCHET, Paris, 1829, p. 33. This letter was ad- 

 dressed to the Imperial Academy of Sciences of St. Petersburg, and was origi- 

 nally published at Leipzig, in 1827. 



