nn: OB \ x ^ 01 i Bl EH ITKMKIM i 



from above downward until I middle of the ;it ! 



In thi- i .o completely separated atria \\ 



have come into exi-t'-nce at a I 



heen forme 1 in the upper part of the p 



ini: downward, an openii: oval.-. \\hi<h 



maintains a conn. -ct ion between the two chambers (fig. 309) up to 

 the time of hirth. The opening has arisen fi- 

 at riorum ha \ ing become thin and broken through at a 

 certain region, or from its l:a\ing heen in.- 

 from the very heginning. as i- the case with the ( 



\\ here it is traversed 

 hy numeious -mail 

 < ritio ' ward- 



the foramen ovule, 

 adapting it -elf to 

 the conditions of the 

 circulation e\i-tin- 

 at the time, becomes 

 >till lar-er. 



The downgi-owtli 

 <f tl:e atrial paili- 



tioll has, li;o; 



the immediate re>nli 

 of >.-puruting the au- 

 ricular c'alial into the 



!id right atrio- 



i.-ulur orifice- 

 (c-i iinpare tig. 308 ok 

 witli tig. 309). Th.- 

 auricular canal, even 

 very soon after its form:i 



from \\itl.out and within. 

 -id.- (fig, 308 ok), it after 

 by being in a manner "\ergrown 



Fig. 909. -Pottanor [dorsal] htlf of the be&rt of 

 embryo of the fifth week, eut open, after Hit. 



n, lower 



(poeterior) part of the atrial partition (wptam intermedium , 



. of the *ntu 



eecunihmi, Bui. 

 ralre. 



ptam puriuni; * Etutachiaa 



goes important alterations 

 first visible from 

 pears from view (tig. 309) 

 all sides 1-y 



and therel.y H'L'*' npwunl 



in con.-e.pK nee of a vigorous gr 



Mderul.le thickness. The opening of 



tricle. or the forunun atrio\ ire commune (fg. 310 .! 



now has the form of a fifc> "i left to rigi 



unded on either side by two ridge-like lips (o.ek and v.tk) 

 the atrioventricular \\< of I.IM -. Off the . .1 cushions of 



