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PROCEEDINGS OF TUK ANATOMIC AL AND ANTHROPOLOGICAL 



the left pulmonary artery by means of a patent ductus arteriosus. 

 As regards the veins each twin is provided with its own superior vena 

 eava, but, the inferior venic cava?, just prior to their termination in the 

 auricle, fuse together to form a single vessel. 



Passing next to the consideration of the heart (Fig. 1) there is 

 what at first sight appears to be a single viscus common to both 

 twins. As this apparently single structure contains two auricles, four 



Fig. 1. Diagram of cardiac and vascular abnormalities-. 



auricular appendages and four ventricles, it is fairly certain that there 

 have been two hearts which have become partially fused in the region 

 of the sinus venosus. As just stated there are but two auricles. One 

 of these is a functional right auricle for both twins. Opening into it 

 there are the two superior vena? cavse, the fused inferior vena 1 cava 1 

 and a single coronary sinus. Opening out of it there are the aper- 

 tures of three of the four auricular appendages, and the openings into 

 the right and left ventricles of the heart of the right foetus. There is 



