AND PREGNANCY 359 



574. The blood-vessels of the chord pass to the pla- 

 centa, of whose origin from the flocculent surface of 

 the chorion that is united to the DECIDUA CRASSA, we 

 formerly spoke. Hence we discover how the substance 

 of the placenta is double, the uterine portion derived 

 from the decidua and forming a spongy parenchyma, 

 the foetal arising from the umbilical vessels distributed 

 on the chorion. The increase of the ovum is irre- 

 gular, the smooth part of the chorion growing more 

 rapidly than the flocculent; consequently., the size of 

 the placenta bears a greater proportion to that of the 

 ovum, the shorter the period that has elapsed since 

 conception, and a smaller, as the period of labour 

 approaches. 



As pregnancy advances, its texture becomes more 

 compact ; furrowed and lobular on its uterine surface, 

 and smooth on the inner surface which is covered by 

 the amnion. It varies greatly in size, thickness, figure, 

 and situation, or place of attachment to the uterus; 

 generally it adheres to the fundus; it is destitute of 

 sensibility and true irritability. 



575. Although all agree that the placenta is the chief 

 instrument in the nourishment of the foetus, the true 

 mode of its operation, and its mutual relation to the 

 uterus and foetus, have given rise to great controver- 

 sies in modern times. After all, the truth appears to 

 be this, that no anastomosis exists between the blood 

 vessels of the uterus and of the chord, but that the 

 oxygenised blood which proceeds from the uterus to 

 the portion of the placenta that was originally the 

 decidua crassa, is absorbed by the extreme radicles of 

 the umbilical vein distributed upon the flocculent cho- 

 rion, and carried to the great venous trunk of the 



