198 



Arthur Willey. 



ments). so that when one of them was removed by cutting across 

 the cephalad and caudad constrictions, the appearance presented 



was that sliown in the outline 

 sketch (Fig. A). There is nothing 

 nnnsual in this, but it forms the 

 basis of an arrangement which, 

 as we shall see, does seem to be 

 uncommon. The ends of each 

 utricle project bej'ond the inter- 

 utricular junctions, especially at 

 the end corresponding with the 

 head of the foetus, so that the 

 entire uterine cornu is contorted and 



Fig. A. 



Outline of a single utricle removed 

 from the body, with the niesometric 

 side (M) upwards, showing the openings packed in amongst the other viscera, 



°' "" tÄ'Ä^ wMch the general flexure being directed 



towards the niesometric side. 



On cutting through the thin antimesometric wall of the utricle. 

 the vascular. sub-opaque, brown-coloured blastocyst is exposed, 

 lying free from the uterine wall except towards the side of the 

 mesometrium. On this side. the chorion adheres by concrescence 

 with the uterine mucosa over an area which is shown, by subsequent 

 dissection, to be niuch larger than that occupied by the peduncle of 

 the placenta. The zone of concrescence extends from the level of 

 the head-region of the foetus, round the base of the placental region, 

 to the level of the tail-region; and it includes within its periphery 

 portions of the uterine cavity which communicate with the inter- 

 utricular lumina. By this means the cavity in which the blastocyst 

 lies, is completely shut off from the neighbouring cavities and the 

 lumen of the Uterus in therefore interrupted at each end of each 

 inter-utricular segment. 



E. Assheton (1895, pl. 19, flg. 3) described and figured dia- 

 grammatically a longitudinal section of the blastocyst and uterus of 

 a rabbit, of about the ninth day after fertilisation, showing how the 

 inter-utricular junctions are plugged up by the horns of the blasto- 

 cyst. This is explained (Assheton op. cit. p. 186) as resulting from 

 the hydrostatic pressure within the blastocyst, Owing to the 

 existence of this pressure it is important that after the rupture of 

 the albumen layer the Communications between the cavity of the 

 utricle and the adjoining passages of the uterus should be closed: 

 otherwise the thin wall of the blastocyst could not withstand the 



