xlii CONTENTS. 



PACK 



690. Erectile tissue ... 1116 



691. The nature of erection 1116 



692. The emission of semen 1117 



CHAPTER II. 

 PREGNANCY AND BIRTH. 



SECTION I. 

 THE PLACENTA. 



693. The spermatozoon enters and unites with the ovum . . . 1119 



694. The formation of the decidua 1119 



695. The decidua serotina is transformed into the placenta. The shed- 

 ding of the placenta 1120 



SECTION II. 

 THE NUTRITION OF THE EMBRYO. 



696. The embryo breathes by and feeds upon the maternal blood of the 



placenta 1123 



697. The blood and blood- flow in the umbilical arteries and umbilical 



vein 1124 



698. The amniotic fluid, its nature and origin, its relations to the nutri- 

 tion of the foetus 1126 



699. The transmission of food material from the mother to the foetus . 1128 



700. Glycogen in the fcetus 1129 



701. The movements of the fcetus . * 1130 



702. The digestive functions of the foetus 1130 



703. The foetal circulation towards the close of uterine life . . . 1132 



704. The cause of the first breath 1134 



705. The changes in the circulation taking place at birth . . . 1134 



SECTION III. 

 PARTURITION. 



706. The period of gestation 1136 



707. The events of "labour" 1137 



708. The reflex nature of parturition 1140 



709. The nerves concerned in the act 1141 



710. The causes determining the onset of labour 1142 



-5711. The inhibition of parturition 11 42 



