DIGESTIVE TRACT OF THE CAT. 



19 



order of entrance of the intestines into the abdominal cavity. 

 First, a simultaneous entrance of the two extremities; 

 secondly, an entrance of the jejunum, and thirdly, of the 

 remaining portion of the ileum. 



Formation of the Transverse and Ascend= 



ing Colon. 



The caecum seems to remain in this position, with its mes- 

 enteric border turned dorsad (Fig. 10), until all the intestines 

 have entered the abdominal cavity. It then turns so that 

 its mesenteric border faces caudad, but it still retains its 

 position in the median line of the body. Fig. 11 shows this 

 relation well. It represents the opened abdominal cavity of 

 an embryo 44 mm. All the intestines were of course intra- 

 abdominal. Those portions of the liver which concealed the 

 stomach and duodenum were removed, as well as the spleen, 

 the greater part of the omentum, and the jejunum and ileum 

 with their mesenteries, in order that the exact position and 

 relations of the caecum and colon might be observed. The 

 caecum is seen in the median line close to the pylorus, and 

 rests upon the mesentery of the duodenum. The colon in 

 the first part of its course is closely applied to the greater 

 curvature of the stomach, and then turns caudad between 

 the junction of the duodenum and jejunum on the one hand, 

 and the Wolffian body on the other. The position of the 

 stomach is distinctly more oblique than in the former younger 

 embryos, and it is curious to notice that the terminal portion 

 of the ileum occupies with great regularity the future site of 

 the ascending colon. 



Fig. 12 represents an embryo 65| mm. The dissection 

 is the same as the last; namely, a reuioval of the abdominal 

 waUs, portions of the liver, the spleen, great omentum, and 

 the greater part of the jejunum and ileum with their mesen- 

 teries. The position of the stomach is not very different 

 from that represented in the last plate, but as we shall see 

 later, its obliquity seems to chiefly depend upon the develop- 



