426 JAMES CRAWFORD WATT 



the costal pleura passed on down as parietal peritoneum on the 

 abdominal wall. 



The hernia is thus of the variety known as hernia diaphrag- 

 matica spuria. Cases of hernia diaphragmatica vera have a 

 hernial sac formed of diaphragmatic peritoneum and pleura 

 invaginated into the pleural sac, so that the abdominal viscera 

 are not in reality in the pleural sac. In this case however, there 

 is no hernial sac, but a complete hole through the diaphragm 

 and its coverings. The genesis of this condition I would inter- 

 pret as a persistence of the embryonic pleuroperitoneal passage, 

 the original communication between the pleural and peritoneal 

 cavities, which has not been shut off, due to the failure of the 

 septum transversum to grow back on this side. The left side 

 normally closes a little later than the right (Keibel and Mall, 

 '10) and this may be one factor in the greater prevalence of 

 hernias on the left side. 



This defect in the diaphragm must have had its origin during 

 the development of the structure, and so occurred between the 

 fourth and eighth weeks of intrauterine life, probably, on account 

 of its size, in the first half of this period, say the fifth week, 

 which synchronises exactly with the production of the defects 

 in the limbs and vertebral column. 



The heart has been pushed over entirely to the right side by 

 the other viscera, but apart from its position is quite normal. 

 The left lung shows two lobes, but is extremely small and flat- 

 tened against the mediastinal wall just above the heart. The 

 abdominal viscera are all fairly normal in relation to each other 

 and seem to have been rotated en masse up and over toward 

 the right. The left lobe of the liver is thus vertical, and against 

 the mediastinal wall. The oesophagus comes from behind the 

 upper end of the heart into the stomach and the latter is vertical, 

 the pylorus being in the abdomen. The duodenum lies over the 

 vertebral column and the small intestine runs from it into the 

 pleural cavity, successive coils being piled continuously above 

 the previous loops up to the apex of the cavity, where the 

 gut is reflected down medially. Opposite the lung occurs the 

 junction with the caecum and appendix. The colon descends 



