PULMONARY DIAPHRAGM OF CHICK 873 



the pleuro-peritoneal membrane on either side and converts it into a muscular 

 structure. These two muscular partitions thus form the pulmonary diaphragm. 



H. The Omental Bursa 



In all gnathostomous vertebrates, the mesogastrium is prone to form a 

 primitive pocket, associated with the rotation of the stomach to the right. 

 This pocket is quite prevalent in most gnathostomous embryos from the elas- 

 mobranch fishes to the mammals and is known as the primitive omental bursa. 

 In mammals, the omental bursa is highly developed, and it gives rise to the 

 lesser peritoneal cavity, retaining its connection with the greater peritoneal 

 cavity by means of the foramen of Winslow. The lesser peritoneal cavity in 

 the cat is extensive, filling the entire inside of the omental sac. In the human, 

 however, the distal part of the lesser peritoneal cavity is reduced by the fusion 

 of the omental layers. Though a rudimentary omental bursa is formed in the 

 early embryonic condition of elasmobranch fishes (sharks), it soon disap- 

 pears, so that, in the adult fish, the omental bursa is nonexistent. Figure 

 364E-H presents various stages in the development of the omental bursa in 

 the human embryo. 



I. The Formation of Various Ligaments in the Stomach-Liver Region 



Ligaments are those specializations of the peritoneal tissue which unite 

 various organs with each other or with the body wall. 



1. The Gastro-hepatic and Hepato-duodenal Ligaments. These structures 

 are derivatives of the ventral mesentery between the stomach-duodenal area 

 and the liver. The gastro-hepatic ligament ties the stomach and liver together 

 while the hepato-duodenal ligament unites the duodenum with the liver. 



2. The Coronary Ligament of the Liver. This is the tissue which unites the 

 liver with the caudal face of the septum transversum and in mammals with the 

 later developed diaphragm. Its development is described on page 866. 



3. The Falciform Ligament of the Liver. This unites the liver in the median 

 plane to the ventral body wall and to the septum transversum or diaphragm. 



4. The Gastro-splenic Ligament suspends the spleen from the stomach and 

 it represents a modification of the mesogastrium (see Chapter 17). 



(Note: Ligamentous structures associated with the reproductive organs are 

 described in Chapter 18.) 



Bibliography 



Goodrich, E. S. 1930. Chap. XII in Studies on the Structure and Development of Verte- 

 brates. Macmillan and Co., London. 



Mall, F. P. 1910. Chap. 13, Vol. I, Manual of Human Embryology. Lippincott, 

 Philadelphia. 



