424 THE CIRCULATORY SYSTEM. 



auricles. The ventricular septum is also usually defective. The right ventricle is 

 hypertrophied. 



2. The pulmonary artery is stenosed or closed. Its branches are supplied by the 



FIG. 222. OPENING IN THE VENTRICULAR SEPTUM OF THE HEART INTERVENTRICULAR FORAMEN. 

 The opening is about 5 mm. in diameter, and its edges are formed by fibrous tissue. 



aorta, through the ductus arteriosus. The ventricular septum is defective, the foramen 

 ovale is open, or the auricular septum defective. 



III. The malformation affects the aorta and pulmonary artery after they are more 

 fully developed. 



1. There is stenosis of the aorta between the left subclavian and ductus arteriosus, 

 or just at the opening of the ductus arteriosus. The descending aorta is then a con- 

 tinuation of the pulmonary artery. 



2. The aorta gives off all its branches from the arch, but the descending aorta is a 

 continuation of the pulmonary artery ; or the carotids may spring from the aorta, the 

 subclavians from the pulmonary artery. 



3. The vessels are transposed; the pulmonary artery arises from the left, the aorta 

 from the right ventricle; the pulmonary veins empty into the left, the venae cavse into 

 ihe right auricle; or the veins also may be transposed. The septa are defective. 



IV. The aorta and pulmonary artery are normal, but the cardiac septa are defective. 



1. The foramen ovale remains partly open. This condition may continue through 

 life without ill effects. It has been found by some observers in about one-fifth of their 

 autopsies. 



2. The ductus arteriosus may remain open for many years ; this also may cause no 

 disturbance. 



3. There is a small or large opening in the ventricular septum, usually in its upper 



