498 



THE PHYSIOLOGY OF REPRODUCTION 



that Sduie of the ^•ac■uules were udt yet filled with maternal 1;ilood, 

 but contained a granular coagulum which might, when liljerated, 

 have a ^lig■esti^■e acti\'ity. In either case, the extensive prolifei'ati(jn 

 ul' the tvo]ihol>last a})]ieavs to provide for the alisor})tion of the 

 necrosed tissue around it, as well as for the How of maternal hlood 

 into its lacuna' hy the erosion of superficial capillaries. These two 

 olijects acciiniiilished, tlie greater part of the tr(ipli(]lilastic })rolifera- 

 tiiiii disap])cai-s. 



Mes 



Fi't. I'r2. — Section tliroiigh einbryiiiiic region of ovvnn (after Peters). 

 ( From C \Veb.3ter's Ifiininii I'lai'oUdtioii.) 



/i.Si'li., Enihryouic epiblast ; Ent., embryonic hypoblast; JA'.s'., mesobla.st ; 

 /J.jS'., umbilical ve.sicle ; A.M., anmiotic cavity; Ekt.^ chorionic epibla.st ; 

 Hp., space. 



Immeihatel)' after the exca\atiou of the cavit}' the decidual 

 foiuiation liegiiis. Bef(irc this stage, the changes resemble those 

 that take place during the menstrual period. The ^•essels are dilated, 

 and l)lood extra vasati(jns occur between the cells and intu the lumen. 

 The tissue is (edeuiatnus and sjKingy, and the swollen cells often 

 appear to lie floating free in a fluid (\'. HeTd<el(jm). These changes 

 are especially marked near tlie mum, and tjiey give rise to an 

 elevation which marks the resting-place of an early blastocyst. The 

 mucosa is diherentiatcd into a su])erficial layei', the comimeia, and a 

 deeper layer, the spoiujioxd, in which are the enlarged middle portions 

 of the glands, arterioles, venules, and lymjiliatics. In the compacta 



