300 



EMBRYOLOGY. 



fig. 165 with the cross section shown in fig. 166. In this way there 

 is formed a cavity (bursa omentalis, fig. 166 **), separated from the 

 rest of the body-cavity, which has its opening turned toward the 

 right, whose front wall is formed by the stomach and whose back and 

 lower wall is formed by the mesogastrium (gn 1 , gn 2 ). In the diagram- 

 matic figures 165 A and B the entrance to the bursa is indicated by 

 the direction of the arrows. 



The bursa onientalis (fig. 166 **) moreover acquires a still greater extension 

 from the fact that the liver (Z) has by this time grown into a large gland, and is 

 united to the lesser curvature of the stomach by means of the lesser omentum 



(kn), the development of which 

 we shall treat of later. There- 

 fore the bursa does not open, 

 as in the diagram (fig. 165), in 

 which the liver with its liga- 

 ments is omitted, at once into 

 the common body-cavity at the 

 lesser curvature of the stomach, 

 but first into an ante-chamber 

 (the atrium bursts omentalis),oi 

 the lesser omental pocket, which 

 lies behind the lesser omentum 

 (kn) and the liver (Z). 



nn 



ao 



nn m 



Fig. 166. Diagrammatic cross section through the 

 trunk of a human embryo in the region of the 

 stomach and mesogastrium, to show the formation 

 of the omentum, at the beginning of the third 

 month, after TOLDT. 



nv, Suprarenal bodies ; o, aorta; I, liver; m, spleen ; 

 p, pancreas ; r/n l , origin of the greater omentum 

 (mesogastrium) at the vertebral column ; gn", the 

 part of the mesogastrium which is attached to the 

 greater curvature (gc) of the stomach ; kn, lesser 

 omentum ; gc, greater curvature of the stomach. 

 * Atrium and cavity of the greater omentum. 



The intestinal loop with 

 its mesentery passes through 

 a no less fundamental twist- 

 ing around its place of at- 

 tachment in the lumbar 

 region than the stomach 

 does. The descending 

 and the ascending arms 

 at first lie side by side. 



Then the latter, which becomes the colon (fig. 165), lays itself obliquely 

 over [ventral to] the former, and crosses the beginning of the small 

 intestine (Jc) transversely. Both parts, but especially the small in- 

 testine, continue from the end of the second month to increase rapidly 

 in length and to take 011 a folded condition. Meanwhile the initial 

 part of the colon, or the ccecum (fig. 165 A bid), which exhibits even 

 in the third month a curved, sickle-shaped, vermiform appendage, 

 comes to lie wholly on the right side of the body up under the 

 liver; from here it runs in a transverse direction across [ventral 

 to] the duodenum under [caudad of] the stomach to the region of 

 the spleen, then bends sharply about (flexura coli lienalis) and 



