3 



jejunum and probably a portion of the ileum have entered 

 the abdominal coelom, but there still remain many coils of 

 ileum in the cavity of the umbilical cord. This section shows 

 well what is not at all uncommon, namely, the presence of a 

 large amount of liver in this cavity. 



Fig. 4 is a sagittal section of an embryo 38 millimetres, 

 and is a much more advanced stage of intestinal development. 

 The position of the caecum and colon is not materially altered, 

 but all of the small intestines are here intra-abdominal, with 

 the exception of a coil of ileum situated a few centimetres 

 from the caecum. 



In Fig. 5, a section of an embryo 38f millimetres, all the 

 intestines have left the cavity of the umbilical cord, and there 

 is now nothing contained therein except the vitelline artery 

 and vein. 



To recapitulate — these sections represent five progressive 

 stages of intestinal development : Fig. i shows the normal 

 umbilical hernia to be at its height, for all those divisions of 

 the intestine (that are ever found there) are in the cavity of 

 the cord. 



In Fig. 2 the two extremities of the intestine (the jejunum 

 and colon) are entering the abdominal ccelom. 



In Fig. 3 this entrance has not only been completed, but 

 the entire jejunum is now contained in the abdominal coelom 

 and only a portion of the ileum remains in the ccelom of 

 the cord. 



The entrance of the ileum is almost completed in Fig. 4, 

 as only a short loop of intestine now remains outside of the 

 abdominal ccelom. 



Fig. 5 shows the umbilical ccelom to be void of intestines, 

 and to contain only the vitelline vessels. 



It is evident that before the intestines can enter the abdom- 

 inal coelom, space must be provided for their accommodation. 

 This is accomplished in various ways, which I will mention 

 in their order of importance. 



Naturally the abdominal cavity of an embryo of 38| milli- 

 metres (Fig. 5) will present a greater capacity than that 

 of an embryo of only 15^ millimetres (Fig. i), but at the 



