INTESTINAL TRACT OF MAMMALS. 



459 



and thrown into elaborate subsidiary loops, but ultimately pursues a straight course 

 along the distal portion of its oval expanse of mesentery to join the hind-gut not far 

 from the duodenum. It enters the hind-gut between two very short but symmetrically 

 placed caeca (C and C2). The hind-gut is differentiated into a colic loop (C.L.) and 

 an expanded rectum. The anterior mesenteric vein curves round Meckel's tract in the 

 normal fashion and is joined by a large posterior mesenteric vein. 



Fig. 13. 



Intestinal Tract of Dasrjpus villosus. 

 Lettering as in fig. 12. 



In Basypus villosus (fig. 13) the pattern of the gut and the disposition of the portal 

 veins are practically identical with the condition in Tatusia, although the duodenum 

 is less separated from Meckel's tract. The caeca, however, are definitely paired 

 (C and C2). The same pattern with paired caeca occurs in Basypus minutiis, whilst 

 the condition in Xenurus unicinctus is again similar, except that the caeca, although 

 paired, are vestigial. 



