CHAPTER VI 



PREGNANCY PARTURITION PUERPERIUM 



SUMMARY. 1. Segmentation of the fertilised ovum; formation of the folds 

 of the blastodermic vesicle ; process by which the ovum grafts itself on 

 the uterine mucosa. 2. Formation of the decidua, chorion, and the maternal 

 and foetal placenta. 3. Formation of the amnion, the umbilical vesicle, the 

 allantois and the umbilical cord. 4. Gravid changes in the uterus and other 

 organs of the genital apparatus, and functional modifications of the whole organism. 

 5. Mechanism of uterine contractions and the pains which occur during parturition ; 

 innervation of the uterus ; the internal causes which determine parturition ; the 

 help of the abdominal pressure during the ecbolic pains ; ligature of the cord, the 

 after-birth or secundines. 6. The phenomena of the recovery of the parts, 

 puerperium. Bibliography. 



To complete the interesting subject of the reproduction of the 

 species, it only remains for us to develop the physiological 

 examination of the functions of maternity properly so called; 

 these comprise the phenomena of pregnancy, parturition, the 

 puerperium, and lactation. We have, however, discussed the last 

 function at sufficient length in Vol. II. Chapter IX. when speak- 

 ing of the secretions of the cutaneous glands and the affinity 

 and philogenetic homology between the sebaceous and mammary 

 glands. 



As regards pregnancy, parturition, and the puerperium, we 

 must in this chapter confine ourselves to physiological questions 

 and problems, so as not to encroach upon the practical aspect, 

 which is dealt with in books on obstetrics. 



I. We saw that the fecundation of the ovum or female sexual 

 cell by the spermatozoon or male sexual cell (v. pp. 192-9) is 

 brought about by the conjugation of the male pronucleus with 

 the female pronucleus ; in this way a new and complete nucleus 

 is formed, which represents the germ of the individual to be 

 born. This new nucleus is called the nucleus of segmentation, 

 because from it starts the development of the new being. 

 Directly it is fertilised there commences in the ovum a rapid 

 process of cell multiplication by karyokinesis: the primordial 

 nucleus divides into two parts and the protoplasm collects round 

 them, forming the first spheres of segmentation or Uastomeres. By 

 successive karyokinetic divisions rapidly following one another, 



VOL. v 211 P 1 



