242 



HUMAN EMBRYOLOGY AND MORPHOLOGY. 



before the division takes place four cushions of the endocardium 

 arise at the junction of venticle and aortic bulb (Fig. 200 A). The 

 four cushions — anterior, posterior and two lateral — become cupped 



right 



ant. 



pulm. artery 



Fig 200. — The origin of the semilunar valves. 



A. The four Endocardial Cushions in the Aortic Bulb. 



B. The division of the Lateral Cushions to form two Aortic and two Pulmonary Semi- 



lunar Valves. 



above and valvular. When the aortic septa are formed, each 

 lateral cushion is divided in two, thus forming the two postero- 

 lateral semilunar valves of the pulmonary aorta and the two 

 antero-lateral of the aorta. The anterior and posterior cushions 

 remain as the anterior pulmonary semilunar valve and the 

 posterior aortic valve (Kg. 200 5). 



Remnants of the Foetal Circulation in the Adult. — The 

 nature of these remnants has been already described ; they need 

 be only enumerated here. They are : 



1. The Obliterated Hypogastric Arteries ; 



2. The Umbilicus ; 



3. The Eound Ligament of the Liver ; 



4. The Fibrous Eemnant of the Ductus Venosus ; 



5. The Eustachian Valve ; 



6. The Foramen Ovale ; 



7. The Fibrous Eemnant of the Ductus Arteriosus. 



The Coelom, Splanchnocele or Cavity of the Body Wall. — 



We have already seen that in the primitive blastoderm (Fig. 191) 

 a cleft is formed between the somatopleure and splanchno- 

 pleure. It is highly probable that the mesothelium which 



