lO C. W. M. Poynter 



§ IV. 

 I. MALFORMATIONS ABOUT THE HEART 



A. ANOMALIES OF THE PERICARDIUM 



I. Deficiency. — Entire absence of the pericardium seems to 

 be unknown except in cases of extensive developmental disturb- 

 ances in which the heart is found outside of the thoracic cavity. 

 More or less complete absence of the parietal pericardium is a 

 rare anomaly, a slight ridge or fold on the right of the great ves- 

 sels represents the remains of this layer. In other cases of less 

 pronounced defect the pericardium covers the right half of the 

 heart, while in others the pericardial case is complete except for 

 a small or large foramen on the left causing a communication 

 between the pleural cavity of the left side and the pericardial 

 cavity. The opening is always on the left and, when large, some 

 of these cases have been referred to as cases in which the heart 

 is found in the left pleural cavity. The left phrenic nerve is dis- 

 placed, running down on the inner chest wall parallel to the in- 

 ternal mammary artery. 



The first to suggest an explanation of the anomaly was Keith 

 (1907), who reported a case of small defect and said: "This is 

 clearly a case of patent pleuro-pericardial foramen. Evidently 

 the condition has been produced by the lung bud growing within 

 and expanding the communication between the pleura and the 

 pericardium, for the communication lies immediately ventral to 

 the point at which the lung bud appears." McGarry (1914) 

 points out a difficulty with the above explanation in that the lung 

 bud does not develop until after the separation of the two cavities 

 is complete. He calls attention to the other developmental errors 

 of the coelom in his case and thinks that the whole is due to some 

 early disturbance interfering with the development of the pleuro- 

 pericardial membrane or its anlage. 



Haller (1757) did not believe that such abnormality could 

 occur and Peacock (1856) thought that some, at least, of the 

 reported cases were not true lack of membrane but universal 



