236 



PHYSIOLOGY 



CHAP. 



eventually disappears. The amnion, however, does not come into 

 direct contact with the chorion, because there remains between 

 the two membranes a thin film of mucous tissue (interconnective 

 membrane or tissue) which is merely the residue of the magma 

 reticularis, with which the cavity of the chorion was filled ; at 

 birth all these parts are removed with the after-birth. 



IV. Pregnancy causes notable modifications in the whole of 

 the genital apparatus of the woman, more especially in the uterus, 



FIG. 98. A, embryo measuring 2'15 mm., according to His ; B, embryo measuring 9'S mm., 

 according to Minot. Am, line of attachment of the amnion ; P, abdominal peduncle ; F, 

 umbilical cord ; V, umbilical vesicle ; Ch, chorion. 



which has to receive the product of conception and support its 

 progressive development during the ten lunar months which 

 normally precede parturition. For this reason the wall of the 

 uterus is not merely distended passively as the ovum increases 

 in size, but also undergoes an active eccentric hypertrophy in all 

 its component parts. 



We have already spoken of the proliferation of the uterine 

 mucosa by means of which the decidua and placenta are formed. 

 No less important is the increase in volume of the smooth muscular 

 coats, which, however, unlike the mucosa, is not effected by new 

 formation, but by gradual hypertrophy, so that at the end of 



