No. i.] THE LESSER PERITONEAL CAVITY. 1 79 



cavity is homologous with the lesser peritoneal cavity, and the 

 opening with the foramen of Winslow of mammals. Both right 

 and left cavities are present in the adult. 



In birds it plays a most important part, forming a distinct 

 cavity, homologous with the lesser peritoneal cavity in mammals. 

 At first the cavities are symmetrical, one on either side, but later 

 in the development the left one disappears, and the right grad- 

 ually enlarges to form the lesser peritoneal cavity, while the 

 communication about the hepatic vessels with the greater cavity 

 forms a foramen of Winslow. 



In the lower mammals there are two gastric diverticula (Ravn), 

 but the left is very insignificant and soon disappears. In the 

 higher mammals only the right one is formed, which gradually 

 increases in size to form the lesser peritoneal cavity. 



Clark University, April 6, 1891. 



