402 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



The alae cordis are eleven in number (fig. 49, 50). 



Dorsal Antero-lateral (cd.l) — one pair. Stretching 

 from the dorsal side of each of the antero-lateral corners 

 of the heart to the corresponding corner of the 

 pericardium. 



Ventral Antero-lateral (cd.2) — one pair. Immediately 

 beneath the dorsal antero-lateral hand. Extending from 

 the ventral side of each of the antero-lateral corners of the 

 heart to the corresponding corner of the pericardium. 



Dorsal Postero -lateral (cd.3) — one pair. Extending 

 from the dorsal side of each of the postero-lateral angles 

 of the heart to the corresponding angle of the pericardium. 



Ventral Postero-lateral (cdA) — one pair. Having a 

 similar position to the dorsal postero-lateral hand, but 

 lying immediately beneath it. 



Median Posterior (cd.&\ — A single band arising from 

 the dorsal side of the posterior angle of the heart and 

 stretching across to the posterior angle of the pericardium. 



Posterior (cd.6) — one pair. Arising ventrally from 

 the postero-lateral side of the heart and crossing to the 

 postero-lateral side of the pericardium. 



The walls of the heart are also very muscular, and 

 the cavity of the heart is crossed by numerous strands of 

 muscle. 



The blood enters the heart from the pericardium by 

 means of the Ostia. There are three pairs of ostia — one 

 pair at the anterior end of the dorsal wall of the heart 

 (Figs. 49, 50. a.ost.), one pair at the posterior end of the 

 dorsal wall (p.ost.), and the third pair are found in the 

 lateral walls of the heart — one ostium at each side (Lost.). 

 Each ostium is valved so as to prevent the blood from 

 returning to the pericardium. 



