Congenital Anomalies of the Heart 3 



turb the growth balance between different parts ; this conclusion 

 is supported by the fact that I have been able to produce the same 

 results by growing the eggs in an atmosphere low in oxygen. 

 All of these experiments seem to support the theory presented by 

 Mall, namely, that faulty implantation or uncongenial environ- 

 ment of the ovum is responsible for a large part, at least, of the 

 anomalies, in man, with which we are acquainted. 



In the case of the heart anomalies we must consider the inter- 

 ference with the growth process as a minor one, notwithstanding 

 the later physiological importance of the resulting irregularity, 

 for the majority of cases of cardiac defects reported show no 

 extensive general growth disturbances. It is impossible to say 

 that the factors which produce cardiac anomalies do or do not 

 produce other lesions, but we at least know that no other lesion 

 is always found in conjunction with them. I have shown in a 

 previous paper (1916) that we must consider variations in devel- 

 opment of the aortic arches independently of cardiac disturbances 

 although they* are frequently found associated in the same case ; 

 and likewise we are forced to conclude that each lesion of the 

 heart must be studied separately, although it is the rule to find 

 two or more lesions associated in the same heart. Stated in an- 

 other way, defective ventricular septum and stenosis of the pul- 

 monary artery must be considered as separate defects, notwith- 

 standing that they are frequently in association ; it would seem 

 that even if the same factor produces both lesions its time of 

 action or intensity must be different for each since each may 

 appear alone. 



From time to time the suggestion has been made that heredity 

 plays a part in etiology but I see no evidence that these cases be- 

 long in the group with polydactylism and hemophilia. In the 

 cases where two or more children in the same family have defect- 

 ive hearts it seems to me more reasonable, from the experimental 

 evidence at hand, to look on these cases as due to a diseased 

 uterine mucosa in the mother rather than a defective germ plasm. 



