LEGENDS FOR ALL OF THE FIGURES 



A, atrium 



A.C., atrial canal 



A.Cu., anterior endocardial cushion 



A.F., annulus fibrosus 



Ao., aorta 



A. P., anterior papillary muscle 



B.S., bulbo-spiral band 



A.V.B., atrio-ventricular bundle 



B., bulb 



C.S., coronary sinus 



I.WC, interventricular canal 



F.O. 1 foramen ovale I 



F.O. 2 foramen ovale II 



L.A., left atrium 



L.Cu., left endocardial cushion 



L.O., left venous ostium 



L.P.. large papillary muscle of the 



right ventricle 

 L.R.V., longitudinal bundle of the 



light ventricle 

 L.V., left ventricle 

 M.p.m., medial papillary muscle 

 P., pulmonary artery 

 P.Cu., posterior endocardial cushion 

 P.P., posterior papillary muscle 

 R.A., right atrium 

 R.Cu., right endocardial cushion 

 R.O., right venous ostium 

 R.V., right ventricle 

 S. A ., septum of the atria 

 S.S., sino-spiral band 

 S.V., septum of the ventricle 



V., ventricle 



Fig. 1 Ventral view of the model of an embryo 2 mm. long (No. 391). X 100. 

 The pericardium has been removed from in front of the heart . 



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