INTESTINAL TRACT OF MAMMALS. 199 



vessels, and were severed before the drawing was made from the 

 dissection. 



In the Diprotodont marsupials the gut-pattern remains in a very- 

 simple condition, but the hind-gut is specially elongated. In all 

 the examples tliat I have dissected this elongation affects the 

 region immediately distad of the pendant looj^, and may be in 

 the form of a few wavy expansions or a moi'e concentrated bunch 

 of minor loops. These are all supported by a simple expansion 

 of the mesorectum, and represent gradations from a merely 

 expanded rectum to what would be regarded as a definite ansa 

 coli sinistra. They are mai-ked C.L. in the figures of Diprotodonts 

 given in my former memoir (Mitchell, 1905, figs. 6, 7, & 8) and 

 C.L. 2 in the figures of this communication. Examination of 

 the Wombat and of the Koala have enabled me to ascertain that 

 in these animals another " colic loop " is present. This is marked 

 C.L. 1 in text-figs. 6 & 8, is developed on the distal limb of the' 

 pendant loop, and represents an ansa coli dextra. 



Sub-Class MONODELPHIA. 



(Edentata.) 

 Order Tubulidentata. 

 Family Orycteropodidse. Orycteropus capensis (text-fig. 10). 



In my former communication (Mitchell, 1905) I had to depend 

 on a description given by Flower. Since then I have had the 

 opportunity of dissecting the intestinal tract of an Aard-vark. 

 The proximal part of the gut is marked ofl' as a duodenal region 

 from Meckel's tract. The proximal part of the latter is a tube of 

 nearly even calibre and of very great length (nearly thirty feet), 

 thrown into minor loops arranged round an oval expanse of 

 mesentery and corresponding with the proximal limb and apex 

 of the pendant loop. The first portion of the recurrent limb is 

 nearly straight. The whole tract is drained by the middle 

 mesenteric vein, which curves round the mesentery, receiving 

 numerous tributaries from the minor loops. 



Meckel's tract opens into a relatively large csecvun, the proximal 

 portion of which is expanded and globular. On opening the 

 cjBCum the ileo-ctecal aperture is seen to lie on the summit of a 

 projecting process surrounded by a circular lip that may contract 

 so as to occlude the aperture. A prominent ridge or flap in the 

 wall of the caecum passes from the proximal extremity of 

 the hind-gut in the direction of the ileo-caecal aperture, and 

 suggests a former division of the ctecum into two caecal pouches. 



The first portion of the hind-gut is much expanded and 

 slightly sacculated. It corresponds with the distal end of 

 the distal limb of the pendant loop. The gut, after reaching 

 the point nearest to the duodenum, bends sharply backwards, 

 and is then expanded to form first a definite wide loop and 

 then a set of minor loops, finally ending in a short straight 



